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Mapping human genetic ancestry

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  • 1. MBE Advance Access published July 28, 2007 1 Mapping human genetic ancestry Research Article Ingo Ebersberger1,3,4,5, Petra Galgoczy2, Stefan Taudien2, Simone Taenzer2, Matthias Platzer2 & Arndt von Haeseler1,3,4,5 1 Center for Integrative Bioinformatics of Vienna, Max F. Perutz Laboratories, Vienna, Austria 2 Leibniz Institute for Age Research – Fritz Lipmann Institute, Jena, Germany (FLI/former IMB) 3 University of Vienna, Austria 4 Medical University of Vienna 5 University of Veterinary Medicine Vienna, Austria Correspondence to: Ingo Ebersberger Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories Dr. Bohr Gasse 9, A-1030 Vienna, Austria E-mail: ingo.ebersberger@univie.ac.at Phone: +43-(0)1-79044 4585 Fax: +43-(0)1-79044 4551 Keywords: lineage sorting, species evolution, human speciation, homoplasy, fossil classification © 2007 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • 2. 2 Abstract The human genome is a mosaic with respect to its evolutionary history. Based on a phylogenetic analysis of 23,210 DNA sequences alignments from human, chimpanzee, gorilla, orangutan and rhesus, we present the first map of human genetic ancestry. For about 23% of our genome we share no immediate genetic ancestry with our closest living relative, the chimpanzee. This encompasses genes and exons to the same extent as intergenic regions. We, conclude that about 1/3 of our genes evolved as human specific lineages before the differentiation of human, chimps and gorillas took place. This elegantly explains recurrent findings of very old human specific morphological traits in the fossils record, which predate the recent emergence of the human species about 5 million years ago. Furthermore, the sorting of such ancestral phenotypic polymorphisms in subsequent speciation events provides a parsimonious explanation why evolutionary derived characteristics are shared among species that are not each other's closest relatives.
  • 3. 3 Introduction Reconstructing the evolutionary process that has molded contemporary humans out of the ancestors shared with their closest relatives, the great apes, is one of the key objectives in evolutionary research (Nuttal 1904; Goodman 1962; King and Wilson 1975; Schwartz 1984; Sibley and Ahlquist 1984; Horai et al. 1992; Shoshani et al. 1996; Ruvolo 1997; Satta, Klein, and Takahata 2000; Klein and Takahata 2002). However, with both amount of data and number of studies increasing, the crux of the matter emerges. Regardless of the type of phylogenetically informative data chosen for analysis, the evolutionary history of humans is reconstructed differently with different sets of data (summarized in Ebersberger 2004). The dilemma is best exemplified, when genetic distances are considered for evolutionary studies. The extent of DNA sequence divergence between humans and chimpanzees in combination with various calibration points for the molecular clock places the split of the two species around 6 million years before present (MYBP) (Glazko and Nei 2003; Patterson et al. 2006). This considerably young age of the human species conflicts with at least part of the fossil record on early human evolution (Brunet et al. 2005; Patterson et al. 2006). Moreover, datings obtained from different regions of the human genome vary over a range of more than 4 million years – some placing the human-chimp split as recent as 4 MYBP (Patterson et al. 2006) – where exons seem to support older splits than introns (Osada and Wu 2005). Eventually, when genetic distances are considered to infer the evolutionary relationships among humans and the great apes, even the species genetically most similar to humans varies with the locus under study (Ruvolo 1997; Satta, Klein, and Takahata 2000; Chen and Li 2001; Patterson et al. 2006; Hobolth et al. 2007).
  • 4. 4 To understand why regions in the human genome can differ in their evolutionary history, it needs to be acknowledged that genetic lineages represented by DNA sequences in the extant species trace back to allelic variants in the shared ancestral species (Nei 1987) (Figure 1). In here, these variants persist until they join in their most recent common ancestor (MRCA). Some genetic lineages, however, do not coalesce in the progenitor exclusively shared by humans and chimpanzees. They enter, together with the lineage descending from the gorilla, the ancestral population of all three species, where any two of the three lineages can merge first. Thus, in two thirds of the cases a genealogy results in which humans and chimpanzees are not each other's closest genetic relatives. The corresponding genealogies are incongruent with the species tree. In concordance with the experimental evidences, this implies that there is no such thing as a unique evolutionary history of the human genome. Rather, it resembles a patchwork of individual regions following their own genealogy. The recent availability of a chimpanzee genome draft sequence and its comparison to the human genome has resulted in a genome-wide collection of genetic differences between the two species (The Chimpanzee Sequencing and Analysis Consortium 2005). A subset of these differences forms the genetic background for the specific phenotypic characteristics of humans (Vigilant and Paabo 1999; Varki 2000; Ebersberger 2004). Accordingly, this catalogue of genetic differences has been referred to as the ultimate resource to study human and chimpanzee biology and evolution (Li and Saunders 2005). It is now interesting to determine when in the history of the two species, and on what lineage these evolutionary changes have occurred, (Chou et al. 2002; Enard et al. 2002; Gilad et al. 2003). From this perspective, particularly the issue that a fraction of our genome does not have the chimpanzee as our closest relative, gains new
  • 5. 5 momentum. Neither do we know for a particular human DNA sequence the genetic sister species, nor do we know when the corresponding genetic lineages have separated. However, only an answer to both questions will help to track down the genetic changes that formed contemporary humans and chimpanzees. In the present study, we focus on three aspects: First, what is the fraction of the human genome, and particularly of the genes therein, for which chimpanzees are not our closest relatives, and how are these regions distributed along human chromosomes. To this end, we compare a genome-wide collection of 23,210 human and chimpanzee DNA sequences to their homologs in gorilla, orangutan and rhesus, respectively. Based on a likelihood approach, we first identify those sequence trees that significantly reject chimpanzees as our closest relatives, i.e. sequence trees that are incongruent with the species tree. Second, we re-estimate the splitting times for the human and great-ape lineages and assess the ancestral population sizes of the ancient species shared by humans and chimpanzees from the fraction of incongruent sequence trees. Third, we determine the position of incongruent sequence trees relative to genes and exons in the human genome and discuss the consequences of the complex genetic ancestry of humans for our view on human and chimpanzee evolution.
  • 6. 6 Materials and Methods Data. We downloaded 33,018 alignments of DNA sequences from human, chimpanzee, gorilla, orangutan and rhesus, originating from a large scale shotgun sample sequencing study of a western lowland gorilla (HCGOM data set (Patterson et al. 2006)) from http://genepath.med.harvard.edu/~reich. Data pre-processing. The HCGOM data set is available only as Arachne alignments (Jaffe et al. 2003) of DNA shotgun sequence reads from the four non-human primate species to the NCBI Build 34 human genome assembly. No information on the quality of the individual aligned sequence reads was provided. To utilize this data set nonetheless, a number of pre-processing steps were required. For each Arachne alignment, we first extracted the individual sequence reads from the gorilla and the orangutan, respectively. Sequences from the chimpanzee and rhesus were ignored at this step since we used the assembled genome sequences instead. For each sequence, we retrieved the corresponding source sequence and its quality information from the NCBI trace archive (http://www.ncbi.nlm.nih.gov/Traces). This step excluded 6,459 Arachne alignments from further analysis, since for at least one orangutan sequence we could find no entry in the NCBI trace archive. We next identified start and end of the subsequence that was used in the Arachne alignment in the source sequence. With this positional information, the corresponding base quality substring was extracted. Subsequently, we assembled the gorilla and orangutan sequences separately into contigs using Phrap (http://www.phrap.org). These contigs were then aligned with the human genome sequence (NCBI Build 36) using BLAT (Kent 2002) with setting minScore=300. If more than one BLAT-hit was obtained, the one with the highest score was retained. Human genome sequence positions covered by both gorilla and orangutan
  • 7. 7 sequences were then identified and the corresponding human DNA sequence was extracted with nibFrag (http://www.soe.ucsc.edu/~kent/src/unzipped/utils/nibFrag/) from the Build 36 genome assembly. To obtain the orthologous regions in the chimpanzee and rhesus genomes, we used the pairwise human-chimpanzee and human- rhesus genome assemblies provided at the Human Genome Browser website (Kent et al. 2002). The corresponding DNA sequences together with their base quality information were then extracted from the chimpanzee genome assembly (PanTro2) and the rhesus genome assembly (rheMac2), respectively. Subsequently, we aligned the DNA sequences from the five primate species with ClustalW (Thompson, Higgins, and Gibson 1994). From these multiple sequence alignment we eventually extracted those regions where sequences from all five species overlap. The resulting 30,112 multiple sequence alignments can be downloaded from http://www.cibiv.at/~ingo/mapofancestry. Quality screen. Positions with a Phred value below 20 were masked in the aligned chimpanzee, gorilla, orangutan and rhesus sequences, respectively (Ewing and Green 1998; Taudien et al. 2006). Increasing the threshold to a Phred value of 40 had no significant effect on the outcome of the analysis, but a mere decrease of the number of analyzed position. Alignment regions with a clustering of masked positions are indicative of an overall low sequence quality. To identify and remove such regions, we penalized alignment columns including a masked position with a minimum of -2 (one masked nucleotide) and a maximum of -6 (all non-human nucleotides have been masked) and rewarding unmasked columns with +1. Then we extracted the highest scoring sub-alignment. Only sub-alignments with a length ≥300 bp were further analyzed, leaving 26,909 alignments.
  • 8. 8 Phylogenetic analysis. Phylogenetic tree reconstructions and molecular clock tests were performed with TREE-PUZZLE (Schmidt et al. 2002) using the HKY model of DNA sequence evolution (Hasegawa, Kishino, and Yano 1985) and four rate categories to model substitution rate heterogeneity among sites. Alignments for which the automatic root search implemented into TREE-PUZZLE did not place the root on the rhesus branch were removed from the analysis (leaving 25,500 alignments), as where such alignments for which the molecular clock was rejected on a significance level of 0.05 (leaving 23,210 alignments). Posterior probabilities for the 15 unrooted tree topologies were estimated from the individual likelihoods assuming a uniform prior distribution on the set of trees. The fraction of incongruent sequence trees was assumed to follow a binomial distribution. 95% confidence intervals were assessed using the normal approximation to the binomial distribution. Dating of speciation events. To assess the splitting times of the five species, we first inferred the sequence tree together with its branch lengths from a concatenation of the alignments that did not reject the molecular clock, and for which the root was placed on the rhesus branch. However, splitting times estimated from DNA sequence comparisons predate the historical separation of the species. To minimize this bias, we omitted alignments, where the inferred sequence tree deviates significantly (posterior probability ≥ 0.95) from the species tree. The split of the orangutan 16 MYBP was used to calibrate the molecular clock. Identification of sequence alignments overlapping with human genes. To identify alignments that overlap with genes and exons in the human genome, we compared the alignment position to the position of ‘known genes’ in the human genome as annotated in the Ensembl release 39 (http://www.ensembl.org/Homo_sapiens/index.html).
  • 9. 9 Analysis of GO terms. To investigate whether gene function has an influence on the phylogeny of the gene sequence, we analyzed the representation of GO terms in our data. To this end, we used FATIGO2 (Al-Shahrour et al. 2006) to screen for GO terms that are overrepresented in the fraction of genes, for which at least one exon overlaps with an alignment that significantly supports an incongruent sequence tree. As a reference, we used those genes in our data set to which a sequence tree was mapped that does not differ significantly from the species tree.
  • 10. 10 Results The finished human genome sequence(International Human Genome Sequencing Consortium 2004) has been recently complemented by draft versions of the chimpanzee and rhesus genomes (The Chimpanzee Sequencing and Analysis Consortium 2005); http://www.hgsc.bcm.tmc.edu/projects/macaque), and extensive amounts of whole genome shotgun sequences from the orangutan (ftp://ftp.ncbi.nih.gov/pub/TraceDB/pongo_pygmaeus). In a recent study on the evolutionary origin of humans, this data set has been further extended by 115,152 shotgun sequences determined from randomly chosen regions of the gorilla genome (Patterson et al. 2006). A combination of the sequence information from the five species (chimpanzee, human, gorilla, orangutan, rhesus) lead to more than 30,000 Arachne (Jaffe et al. 2003) alignments (Patterson et al. 2006). This data is used to address the question of our genetic ancestry on a genome-wide scale with a likelihood based approach. Processing of the Arachne alignments (see M&M) provided a total of 23,210 clock-like evolving DNA sequence alignments of five species each, summing up to a total of 14,512,620 compared nucleotide positions (Table 1). Contrasting phylogenetic signals in the data We first assessed the fraction of sequence trees that is incongruent with the species tree. To this end, we calculated the likelihoods for all fifteen unrooted tree topologies (Felsenstein 1981) for each individual alignment. If we take the maximum likelihood tree at face value to represent the phylogeny of the alignment, then 9,343 (40%) of the sequence trees are incongruent with the species tree (Table 2). Among these trees, the majority (8,630) places the orangutan basal to humans and the African apes. The
  • 11. 11 incongruence with the species tree is restricted to the subtree connecting humans, chimps and gorillas. The remaining 713 alignments do not recover the monophyly of humans, chimpanzees and gorillas. Alas, the five species under study, and thus their DNA sequences, are in part very closely related. As pointed out (Takahata and Satta 1997; Yang 2002), this may result in an erroneous reconstruction of the sequence tree, since different branching patterns have similar likelihood values. The likelihood mapping plot (Strimmer and von Haeseler 1997) in Figure 2 gives an impression about the extent of phylogenetic information in the data with respect to the resolution of the subtree connecting humans, chimpanzees and gorillas. Figure 2C shows that ~40% of the alignments provide no clear support for a single branching pattern. Consistent with the prediction that the inclusion of alignments with no clear phylogenetic signal leads to an overestimation of the fraction of incongruent sequence trees (Yang 2002), we observe an increasing proportion of incongruent sequence trees with decreasing phylogenetic information in our data (Supplementary Figure 1). To identify the subset of our data significantly supporting only a single phylogeny, we consider only sequence trees that are supported with a posterior probability of at least 95%. This leaves us with 11,945 phylogenetically informative alignments (Table 1 and Table 3). Among these, 23.0% (95% confidence interval (c.i.): 22.2 – 23.8%) support a closer relationship of gorilla to either humans or chimpanzees, while they recover the monophyly of the three species. Trees where the gorilla is placed closer to the chimpanzee, and trees with a human-gorilla sister group are observed equally often (1,369 and 1,361, respectively). Note that still 0.6% (95% c.i. 0.4 – 0.7%) of the resolved sequence trees place the orang within the human-chimp-gorilla subtree.
  • 12. 12 Subsequently, we checked whether the amount of incongruent sequence trees varies in different subsets of the human genome. First, we considered alignments that overlap with genes and exons, respectively. No significant difference in the frequency of the individual tree topologies compared to the genome-wide average is seen (Table 3). This figure changes when we assess the fraction of incongruent sequence trees separately for the individual chromosomes (Table 1 and Figure 3A). Values range between a low of 9.9% (95% c.i. 7.6 – 12.8%) for human chromosome X to a high of 29.3% (95% c.i. 26.1 – 32.8%) for human chromosome 8. A one factorial ANOVA and a subsequent Bonferroni posttest rejected the hypothesis that all autosomes show the same mean fraction of incongruent sequence trees (p < 0,01). However, in a subsequent pair-wise comparison, only chromosomes 7 and 8, displaying the smallest and largest proportion of incongruent trees, respectively, differ significantly. Including the X chromosome into the analysis revealed that the fraction of incongruent sequence trees on the sex chromosome is significantly different to that observed on all human autosomes, except for chromosome 7 and 22. The palaeo-demographic history of humans and chimpanzees The intertwined genetic relationships between humans, chimpanzees and gorillas allow conclusions about the palaeo-demographic histories of these species. Under a model of random genetic drift, the probability, p( H ,C )G , to observe a congruent human- chimpanzee-gorilla sequence tree depends on the effective size, N e (HC) , of the ancient ! population, from which humans and chimpanzees emerged, and the time in years, T( HC ) , ! the progenitor species has persisted. More precisely, "(T( HC ) /(2N e ( HC )#g ( HC ) )) ! p( H ,C )G = 1" 2 e 3 , !
  • 13. 13 where g( HC ) is the generation time (Nei 1987; Pamilo and Nei 1988). We estimate p( H ,C )G to be 0.765 for the autosomes and 0.901 for the X chromosomes. To estimate ! N e , we need to infer T( HC ) . To this end, we determined the genetic distances between ! the species from a concatenation of our alignments. The analysis of a total of ! 12,222,543! nucleotide positions from the human autosomes results in the phylogenetic tree shown in figure 4A. The branch lengths of this tree were transformed into absolute time estimates by assuming that the orangutan lineage emerged 16 million years ago (Goodman et al. 1998; Glazko and Nei 2003). This obtains that gorillas branched off 7.8 MYBP, and the separation of humans and chimpanzees ensued 2.1 million years later. Assuming a generation time of g( HC ) = 20 years, our estimates of T( HC ) and p( H ,C )G averaged over the autosomes result in an effective population size for the human- chimpanzee ancestral! ˆ ! ! species of N e (HC) = 49,000 (95% c.i. 48,000 – 51,000). ˆ However, N e (HC) is substantially smaller when we use the X chromosomal data to ! ˆ assess p( H ,C )G ( N e (HC) = 28,000; 95% c.i. 24,000 – 32,000). An overview of the ! ˆ N e (HC) variation among the individual human chromosomes is shown in Figure 3B. ! ! ! The evolutionary age of human genetic lineages Subsequently, we identified those human genes in our data set, for which exonic sequence overlapped with regions with an incongruent genealogy. A total of 125 genes were identified this way, 63 overlapped with regions placing chimpanzees closer to gorillas, and 62 with regions supporting a human-gorilla grouping. A detailed list is given in the online supplementary material (Supplementary Table 1).
  • 14. 14 Discussion The evolutionary history of humans and the genetic relationships to their next closest relatives, the great apes, has been central to numerous studies in the past. Still, the picture about how and when humans emerged as a species from the common ancestor shared with chimpanzees remains fragmentary. In the present study we have reanalyzed a data set of 23,210 alignments of human, chimpanzee, gorilla, orangutan and rhesus DNA sequences from randomly chosen regions of the human genome (Patterson et al. 2006) using maximum likelihood. We infer that for about 23% of our data set chimpanzees are not the closest genetic relatives to humans. This figure is substantially smaller than previous estimates in the range of 40% based on far smaller data sets, and where the varying extents of phylogenetic information in the data was not taken into account (Satta, Klein, and Takahata 2000; Chen and Li 2001). However, it lies well in the range of the 18 – 29% suggested by (Patterson et al. 2006), who used a maximum parsimony approach to analyze the data. Nonetheless, one simplifying assumption in our analysis needs to be taken into account that could bias the outcome of our analysis towards a slight underestimation of the fraction of incongruent trees. Given the limited length of the alignments available, and the resulting average low number of phylogenetic informative positions, we had to assume that DNA sequences in the individual alignments have evolved according to a single sequence tree. Thus, recombination, which facilitates the alternation of varying phylogenies along a DNA sequence, had to be ignored. Evidence exists that regions in the human genome with an incongruent genealogy might be short compared to our average alignment length (630 bp) (Hobolth et al. 2007). In such a case, the phylogeny is likely to change within an alignment that contains incongruent sites. As a consequence, the alignment has an
  • 15. 15 increased probability to be phylogenetically uninformative in our analysis. To assess the extent of underestimation, we analyzed the fraction of parsimoniously phylogenetic informative sites with respect to the human-chimp-gorilla subtree in our entire data set. 23,510 sites support the grouping of humans and chimpanzees, while 9,596 sites (29%) suggest an incongruent genealogy. Since this approach assumes that every site evolves independently, and neglects homoplasy, which mimics an incongruent generalogy, 29% comprises the upper boundary of incongruent sites in our data set. A map of our genetic ancestry In view of the random character of the sampling strategy, our results indicate that roughly one quarter of our genome shares no immediate ancestry with chimpanzees. To get an impression about the spatial distribution of such regions, we mapped the resolved sequence trees onto the human chromosomes (Figure 5 and Supplementary Figure 2). Incongruent sequence trees are present on all autosomes as well as on the X chromosome, and display no general tendency for a regional clustering. Thus, these chromosomes emerge by and large as random assemblies of regions owning a distinct evolutionary relationship to the great apes. Re-shuffling of parental chromosomal loci during meiosis has presumably acted to decouple the evolutionary histories of genetic regions located on the same DNA molecule (Paabo 2003; Hobolth et al. 2007). However, the probability to observe an incongruent sequence tree seems not to be the same throughout our genome. When we asses the fraction of incongruent sequence trees for the individual human chromosomes, values range between 18% and 29% with a mean of 23.6% for the human autosomes, and it is as low as 10% for the human X chromosomes (c.f. Figure 3B). For the autosomes, we can only speculate about the
  • 16. 16 causes leading to the observed variation in the fraction of incongruent trees. Likely explanations fall into two categories. The first one assumes that all autosomes share the same fraction of sites with an incongruent genealogy. However, the power to detect these sites differs significantly for each chromosome. As one possible scenario, we could imagine that recombination patterns may have varied among chromosomes in the human-chimpanzees ancestor. As a consequence, sites following an incongruent genealogy might be more scattered, and thus more difficult to detect in our analysis, for one chromosome than for another. However, we find no correlation between the fraction of incongruent sequence trees and the fraction of unresolved trees for the individual autosomes. The second categorie of explanations assumes that the individual autosomes differ significantly in their fraction of sites with an incongruent genealogy. Such a deviation from the neutral model detailed in Figure 1 could point toward the effect of selection. For example, regions under balancing selection (Charlesworth 2006) in the common ancestor of humans and chimpanzees have a higher probability to retain ancestral polymorphisms, and thus, would show up as regions in the human genome with an increased fraction of incongruent sequence trees. In turn, selective sweeps (Voight et al. 2006) in the human-chimp ancestral species would remove any ancestral polymorphisms, and thus result in islands in our genome, where incongruent sequence trees are depleted. Notably, in Figure 5 and Supplementary Figure 2 individual genomic regions can be seen that are conspicuously free of incongruent sequence trees. In summary, whatever causes the observed variation in the fraction of incongruent sequence trees, we can think of no influence resulting in an overestimation of this fraction. From this perspective, our figure of 23.6% incongruencies serves as a conservative baseline for the entire human autosomes. Any region deviating
  • 17. 17 significantly from this figure is indicative of having an evolutionary history that differs from the genome average. The situation is, on a first sight, different for the human X chromosome. So far, we have not taken into account its lower effective population size, which is only ¾ that of the autosomes. Thus, a significant lower observation frequency of incongruent sequence trees on the X chromosome to the autosomes is not surprising. Population size of the species ancestral to humans and chimpanzees From the observed frequency of incongruent sequence trees on the autosomes, we conclude that the species from which humans and chimpanzees emerged had a population size in the range of 49,000. This value appears in agreement with previous studies that chose different approaches to this question (Wall 2003; Hobolth et al. 2007). The estimate, however, essentially depends on the choice of the individual species’ generation times and the calibration of the molecular clock. For example, Hobolth et al. (2007) used a mean generation time as high as 25 years for all extant and ancestral species, a value that can be safely considered unrealistic. This choice essentially implies that their data supports a substantially higher effective population size of the predecessor species of humans and chimpanzees than their stated figure of 50,000. Our assumption of g( HC ) = 20 years can still be considered as too high, and might reflect more the generation time of contemporary humans rather than that of the ! ˆ ancestral species we shared with chimps. Reducing g( HC ) to 15 years increases N e (HC) to 67,000 (95% c.i. 65,000 – 70,000). On the other hand, our dating for the split of the ! ! orangutan lineage (16 MYBP) used for calibrating the molecular clock might be too far back in time. A recent study on estimating the time points when the individual primate
  • 18. 18 lineages have emerged, places the split of the orangutan lineage 13 MYBP (Glazko and ˆ Nei 2003). Based on this splitting time, T( HC ) reduces to 1.7 MY. With 20 years as an ˆ estimate for g( HC ) , N e (HC) equals 41,000 (95% c.i. 39,000 – 42,000). Taking into ! account both our ignorance of g( HC ) and T( HC ) , we conclude that the effective population ! ! size of the species ancestral to humans and chimpanzees was 49,000 with a range from 39,000 to 69,000. A ! ! comparison of these estimates to the effective population sizes assessed for the contemporary human and great ape populations (Kaessmann et al. 2001; Yu et al. 2001) reveals that considerably little has changed in the demographic history of chimpanzees and gorillas. In contrast, an about five fold reduced effective population size is observed for extant humans and bonobos. This adds a further line of evidence that humans – as must have bonobos – experienced a severe demographic bottleneck in their recent evolutionary history (Kaessmann et al. 2001). The peculiar evolutionary history of the human X chromosome The effective population size of the species ancestral to humans and chimpanzees estimated from the fraction of incongruent sequence trees observed on the X chromosome is 28,000 (95% c.i. 24,000 – 32,000). This value is significantly smaller than the expected N e,X (HC) = 3/4 " 49,000 = 36,750 , based on the analysis of the autosomal data. Accordingly, the reduction in the observation frequency of incongruent ! sequence trees on the X chromosome compared to the autosomes cannot be explained by its lower effective population size alone (binomial test: p < 0.0001). Moreover, when we assess the splitting times from the concatenated X chromosomal alignments, these results also differ from those obtained from the autosomal data (Figure 4B). The split of humans and chimpanzees is dated more recent (5.4 MYBP), and the time the common
  • 19. 19 ancestor of humans and chimpanzees has existed, is about 700,000 years longer than the corresponding estimate from the autosomes. When we use the dating from the X chromosomal sequences to assess N e,X (HC) from the fraction of incongruent sequence trees on the X chromosome, we estimated an ancestral population size of 37,000 (95% ! c.i. 32,000 – 43,000). This value is almost exactly the expected three quarters of the population size estimated from the autosomes. Thus, the prolonged time span for the human-chimpanzee ancestor for the X chromosome suffices to explain its reduced fraction of incongruent sequence trees. To date, we can only speculate about the underlying cause of the marked difference in the evolutionary history of the autosomes and the X chromosomes. Re-hybridization of human and chimpanzees subsequent to their initial separation into two different species, as suggested in (Patterson et al. 2006) and (Osada and Wu 2005), might serve as one explanation. Alternatively, recurrent selective sweeps in the human-chimp ancestral population occurring more frequently on the X than on the autosomes – due to the direct exposition of recessive mutations to selection in males – could result in a similar figure. The removal of ancestral polymorphisms by selective sweeps has two effects. First, it reduces the fraction of incongruent sequence trees. Second, it reduces the coalescent time for human and chimpanzee genetic lineages. By that it places the human-chimp split inferred from their genetic distances more recent, and thus it prolongs the estimated time span the ancestral species to humans and chimpanzees has existed. However, alternative explanations might exist. In this context, the distribution of incongruent sequence trees on the X chromosome might be informative. If repeatedly selective sweeps acted on the X chromosome we would expect extended regions on the X that are depleted of incongruent sequence trees. Presumably, no such clustering is expected when
  • 20. 20 hybridization between humans and chimpanzees would have caused the observed scenario. Unfortunately, the number of 50 incongruent sequence trees we could map to the X chromosome is yet too small to allow for this analysis. The evolutionary age of the human genome Twenty three percent of our genome sharing no immediate ancestry with chimpanzees has a further interesting implication. Necessarily, the corresponding genetic lineages must have split from their MRCA shared with any other species already prior to the speciation of the gorilla. Thus, a substantial part of the human genome began to evolve – in a today's point of view – 'human specific' way long before humans emerged as a species. Obviously, in our analysis we observe only 2/3 of such 'old' genetic lineages (figure 1, dashed graphs), since the sequence trees of the remaining 1/3 agree with the species tree. Taking this into account, our results suggest that the ancestry of as much as 35% of our genome dates back to the ancient species we shared with the gorilla. What is the relevance for the evolution of functional sequences in the human genome? We observe incongruent sequence trees with frequencies around the genome-wide average in regions covered by genes and exons (c.f. Table 3 and Supplementary Table 1). Furthermore, no overrepresentation of certain GO terms in the list of genes for which an incongruent sequence tree overlapped with an exon was observed (data not shown). Jointly, this suggests that the evolutionary relationships of human and chimpanzee sequences are by and large independent from the presence and function of genes and exons. From this figure, we conclude that roughly one out of three genes (35%) contain at least parts, which evolved 'human specific' already in the progenitor species of humans, chimpanzees and gorillas. The consequences are intriguing.
  • 21. 21 Despite extensive studies on early human evolution, it is still unclear when in our evolutionary history we split from the ancestral species shared with the chimpanzees. Particularly puzzling in this context is the apparent discrepancy between the dating of this split based on genetic evidences, and the age of fossils, which have been – due to their display of certain human specific characteristics – assigned to a hominid species, that is a species more closely related to humans than to chimpanzees. The extent of genetic differences between humans and chimpanzees usually places the split of humans and chimpanzees around 5-6 MYBP (Chen and Li 2001; Glazko and Nei 2003; Kuroki et al. 2006), with a variation of at least 4 million years across the genome (Barton 2006; Patterson et al. 2006). However, the current interpretation of the fossil record argues for the presence of hominids already 5.8 MYBP (Orrorin tugenensis; Senut et al. 2001, and Ardipithecus kadabba; WoldeGabriel et al. 2001), and presumably as early as 6.5 – 7.4 MYBP (Sahelanthropus tchadensis; Brunet et al. 2005). Hitherto only a single attempt has been made to reconcile this discrepancy. Patterson et al. (2006) propose a circuitous evolutionary scenario, where humans and chimpanzees separated initially prior to the emergence of Sahelanthropus tchadensis, explaining both the fossil record and the evolutionary older parts of the human genome. A later gene flow between the two species facilitated by re-hybridization with the chimpanzee was then proposed to explain the evolutionary younger fraction of our genome. Our results, however, provide a far more parsimonious explanation. The varying evolutionary ages of the human genome are to a large extent simply a consequence of the stochastic nature of the coalescent process determining the genealogy of human and chimpanzee genetic lineages (Barton 2006). More importantly, in view of the age of certain human genetic lineages (c.f. Supplementary Table 1), it
  • 22. 22 seems mandatory to consider that a number of phenotypic characteristics nowadays judged as 'human specific' inventions (apomorphies) existed de facto already in the ancestral species of humans and chimpanzees. It is only because the corresponding genetic lineages were lost in our next relatives that these characters became confined to humans. The unequivocal assignment of fossil remains to a species more closely related to humans than to chimpanzees based on the presence of certain 'human specific' apomorphies should, therefore, be taken with a grain of salt. A similar point can be made in context of the recent discussion concerning the position of Australopithecus afarensis in the hominid phylogeny (Rak, Ginzburg, and Geffen 2007). This species has been proposed as the common ancestor of later hominines (Johanson and White 1979; White et al. 2006) including the genus Homo. However, the observation of an evolutionary derived ramal morphology of A. afarensis, resembling the status in gorilla, while contemporary humans and chimpanzee display the ancestral state, was taken as evidence to exclude A. afarensis from human ancestry (Rak, Ginzburg, and Geffen 2007). The problem in using apomorphies for the reconstruction of phylogenetic relationships, however, extends beyond the classification of fossils. A non-negligible fraction of human genes is expected to share an immediate ancestry with the gorilla, or with the common ancestor of chimpanzees and gorillas. Since gene products essentially define the phenotype, we can expect a certain proportion of derived morphological characters to support the sister grouping of humans and gorillas, or chimpanzees and gorillas, respectively. This expectation is corroborated by comparative morphological studies between humans, chimpanzees and gorillas (Shoshani et al. 1996; Collard and Wood 2000). For a number of phenotypic characters, either humans or chimpanzees share the
  • 23. 23 derived character state with other great apes, while the ancestral character state is still seen in the respective other species (Supplementary Table 2). To water down the apparently contradictory character of such data, taxonomists proposing the human- chimp sister group status employed additional evolutionary scenarios, e.g. the same derived character state might have arisen twice independently during evolution (Pilbeam 1986; Lockwood, Kimbel, and Lynch 2004). Opponents of the human-chimp grouping, on the other hand, exploited such observations to promote alternative phylogenies of humans and the great apes (Schwartz 1984). However, our genome wide comparison of DNA sequences between human and great ape species provides an alternative explanation, which easily resolves the discrepancy between the various schools favouring one over the other phylogeny. The random sorting of ancestral genetic polymorphisms that have a phenotypic polymorphism associated, can explain why synapomorphies can be shared among species that are not each other's closest relatives. In summary, our study highlights the extent and implications of the intertwined genetic relationships between humans, chimpanzees and gorillas. Clearly, a comprehensive understanding of how humans evolved their unique characteristics, which distinguishes them from all other extant species, depends essentially on our knowledge of the evolutionary history of our genes. From this perspective, an extensive sequencing of the gorilla genome will be required to make full use of the chimpanzee genome sequence on the way towards a map of our genetic ancestry.
  • 24. 24 Acknowledgement The authors wish to thank Heiko A. Schmidt and Vinh Le Sy for help in the Maximum Likelihood Analyses, Tanja Gesell and Steffen Klaere for helpful comments on the manuscript. The work was in part supported by the German National Genome Network grant 01GR0105. Financial support from the Wiener Wissenschafts- und Technologie- Fond (WWTF) is also acknowledged.
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  • 31. 31 Table 1 Data per human chromosome Chr unresolved congruent incongruent incongruent P!(HC)c (95% THCd treesa (bp) trees (bp) trees (bp) trees c.i.) !(HC)b (bp) 1 875 746 222 216 0.225 (0.199 - 2.09 (534,348) (489,475) (141,003) (137,014) 0.252) 2 1083 784 258 250 0.242 (0.217 - 2.05 (662,878) (503,638) (164,281) (158,893) 0.269) 3 844 689 224 216 0.239 (0.212 - 2.04 (511,478) (439,967) (143,461) (138,385) 0.268) 4 800 623 240 234 0.273 (0.244 - 2.17 (485,332) (401,151) (152,474) (148,818) 0.304) 5 793 593 164 163 0.216 (0.188 - 2.02 (482,433) (384,869) (103,521) (102,841) 0.246) 6 681 562 166 162 0.224 (0.195 - 2.09 (413,617) (362,229) (108,306) (105,457) 0.256) 7 622 494 122 116 (75,690) 0.190 (0.161 - 2.07 (376,931) (322,539) (79,787) 0.223) 8 652 489 206 203 0.293* (0.261 - 2.01 (389,957) (309,131) (133,763) (131,967) 0.328) 9 430 321 95 (62,077) 94 (61,431) 0.227 (0.189 - 2.10 (263,814) (206,528) 0.269) 10 532 451 129 126 (78,550) 0.218 (0.187 - 2.07 (321,819) (297,923) (79,779) 0.254) 11 527 427 139 135 (87,587) 0.240 (0.207 - 2.11 (323,719) (271,289) (90,011) 0.277) 12 534 434 126 123 (77,411) 0.221 (0.188 - 2.13 (316,150) (279,528) (79,077) 0.257) 13 413 339 100 100 (62,176) 0.228 (0.191 - 2.15 (247,541) (218,931) (62,176) 0.269) 14 335 278 106 104 (66,273) 0.272 (0.230 - 2.11 (205,718) (179,268) (67,427) 0.319) 15 352 264 87 (57,416) 83 (54,871) 0.239 (0.197 - 2.01 (212,254) (170,824) 0.287) 16 294 220 53 (33,605) 53 (33,605) 0.194 (0.152 - 1.98 (177,154) (142,967) 0.245) 17 254 204 61 (40,574) 59 (39,189) 0.224 (0.178 - 1.99 (151,447) (130,653) 0.279) 18 333 279 95 (60,631) 94 (60,187) 0.252 (0.211 - 2.18 (203,240) (181,758) 0.298) 19 140 79 (50,123) 28 (17,064) 26 (15,821) 0.248 (0.175 - 1.96 (83,264) 0.338) 20 213 225 63 (41,026) 62 (40,480) 0.216 (0.172 - 2.25 (130,284) (142,255) 0.267) 21 122 101 40 (24,768) 40 (24,768) 0.284 (0.216 - 2.07 (75,791) (63,346) 0.363) 22 83 (47,862) 90 (57,120) 21 (13,672) 21 (13,672) 0.189 (0.127 - 2.11
  • 32. 32 0.272) X 354 455 52 (33,006) 50 (31,988) 0.099* (0.076 - 2.82 (207,153) (294,019) 0.128) total 11,266 9,147 2,797 2,730 0.230 (0.222 - 2.08 (6,824,184) (5,899,531) (1,788,905) (1,747,074) 0.238) a The maximum likelihood tree has a posterior probability below 0.95. b Incongruent sequence trees that differ from the species tree only in the branching order of humans, chimpanzees and gorillas (!(HC)). c Probability to observe an !(HC) tree, and the corresponding 95% confidence intervals. Chromosomes that differ significantly from the genome-wide average of 0.230 are marked with an asterisk. d Estimated time span the shared ancestral species to humans and chimpanzees has existed in MY. For this column, ‘total’ represents the estimate obtained from the concatenation of only the autosomal sequences.
  • 33. 33 Table 2 Number of alignments in support of the 15 sequence tree topologies featuring the monophyly of the great apes. All (%) Genea (%) Exonb (%) 174 (0.75) 70 (0.72) 15 (1.06) 13,869 (59.75) 5,869 (60.39) 805 (57.05) 205 (0.88) 101 (1.04) 23 (1.63) 15 (0.06) 5 (0.05) 3 (0.21) 29 (0.12) 14 (0.14) 0 (0) 50 (0.22) 17 (0.17) 3 (0.21) 25 (0.11) 12 (0.12) 2 (0.14) 20 (0.09) 7 (0.07) 1 (0.07) 41 (0.18) 19 (0.20) 5 (0.35) 4,140 (17.84) 1,650 (16.98) 242 (17.15) 43 (0.19) 23 (0.24) 5 (0.35) 64 (0.28) 26 (0.27) 8 (0.57) 4,490 (19.34) 1,881 (19.36) 289 (20.48)
  • 34. 34 14 (0.06) 5 (0.05) 2 (0.14) 33 (0.14) 19 (0.20) 8 (0.57) a alignments that overlap with the position of a gene in the human genome. b alignments that overlap with the position of an exon in the human genome.
  • 35. 35 Table 3 Number of alignments significantly* supporting the 15 sequence tree topologies featuring the monophyly of the great apes. All (%) Genea (%) Exonb (%) 20 (0.17) 8 (0.17) 2 (0.32) 9,148 (76.58) 3,814 (78.85) 487 (78.93) 19 (0.16) 10 (0.21) 2 (0.32) 0 0 0 1 (0.01) 0 0 5 (0.04) 2 (0.04) 0 0 0 0 0 0 0 4 (0.03) 1 (0.02) 0 1,369 (11.46) 504 (10.42) 63 (10.21) 13 (0.11) 6 (0.12) 1 (0.16) 5 (0.04) 0 0 1,361 (11.39) 492 (10.17) 62 (10.05)
  • 36. 36 0 0 0 0 0 0 * posterior probability ≥ 0.95 a alignments that overlap with the position of a gene in the human genome. b alignments that overlap with the position of an exon in the human genome.
  • 37. 37 Figure 1 (A) The distinct evolutionary histories of species and their genes. The species tree is drawn in black. T1 and T2 denote the speciation events of humans and chimpanzees, and of gorillas, respectively. Human and chimpanzee genetic lineages can coalesce in their most recent common ancestor (MRCAHC) in the progenitor exclusively shared by the two species (red solid sequence tree). Under a model of random genetic "T( HC ) /(2N e #g ) drift, this occurs with p( H ,C ) = e , where T(HC) is the time span between T1 and T2, Ne is the effective population size of the ancestral species, and g is its generation time. The branching pattern of the resulting sequence tree is congruent to the species ! tree. For the dashed sequence trees, human and chimpanzee genetic lineages fail to coalesce in the exclusive ancestor of both species. In the ancestral species shared by humans, chimpanzees and gorillas any two of the three lineages can join first. The green graph depicts the coalescent event resulting in a common ancestry of chimpanzees and gorillas (MRCACG). The remaining two branching patterns, (H,C)G and (H,G)C, are shown in (B) and (C), respectively. Figure 2 Likelihood mapping plot of the five-species alignments supporting the monophyly of humans and the great apes. (A) Each point in the equilateral triangle represents a single alignment. The lengths of the perpendiculars from any point to the triangle sides are equal to the posterior probabilities each of the three topologies of the subtree connecting human, chimpanzee and gorilla ((H,C)G; (H,G)C; (C,G)H) is supported by the corresponding alignment(Strimmer and von Haeseler 1997). The closer a point is located to one of the three edges, the higher the support for the respective phylogeny. (B) Fraction of the data for which the support for the respective sequence tree is largest. (C) The area of the triangle is separated into seven regions reflecting different phylogenetic information contents of the data. Alignments located in the central area fail to resolve subtree. Alignments located in the corner areas support the corresponding sequence tree. The remaining three regions contain those alignments
  • 38. 38 for which it is not possible to decide between two of the three topologies. Numbers represent the percentage of the data set located in the seven areas. Figure 3 (A) Variation of the probability to observe a sequence tree significantly rejecting the human-chimp sister group (P!(HC)) among the human chromosomes. (B) Variation of the effective population size estimate of the human-chimp ancestral species among the human chromosomes. Bars denote the 95% confidence interval. Figure 4 Sequence tree of the five species under study reconstructed from the autosomal sequences (A) and X chromosomal sequences (B), respectively. Splitting times were dated assuming the split of the orangutan lineage 16 million years before present (MYBP). Trees are not drawn to scale. Figure 5 Distribution of resolved sequence trees recovering the monophyly of humans and the great apes along human chromosomes 1 and 2. Supplementary figure 1 Fraction of incongruent sequence trees in subsets of our data. The fraction of incongruent sequence trees diminishes with increasing support of the maximum likelihood tree by the underlying alignment. Supplementary figure 2 Distribution of resolved sequence trees along human chromosomes 3 to X. (H,C)G are represented in red, (H,G)C trees in blue and (C,G)H trees in green. Supplementary table 1 Incongruent sequence trees located within human genes. Shown are those genes for which at least one exon overlaps with an alignment supporting an incongruent sequence tree. Supplementary table 2 Derived morphological characters supporting varying human- chimpanzee-gorilla phylogenies.
  • 39. 39 Figure 1
  • 40. 40 Figure 2
  • 41. 41 Figure 3 A B
  • 42. 42 Figure 4 A B
  • 43. 43 Figure 5
  • 44. 44 Online-only Information Supplementary Table 1 Exons located in alignments that support an incongruent sequence tree Ensembl Refseq_ID Sequence Tree Posterior Exon Description Transcript ID Probability Type ENST00000307493 NP_443188 (((C,G)H)O)R) 1 coding acyl-CoA synthetase medium- chain family member 1 ENST00000326303 NP_689544 (((H,G)C)O)R) 1 coding Acyl-coenzyme A thioesterase 4 ENST00000265512 NP_000661 (((C,G)H)O)R) 1 coding Alcohol dehydrogenase 4 ENST00000382410 NP_697020 (((C,G)H)O)R) 1 coding Beta-defensin 125 precuror ENST00000262717 NP_114097 (((H,G)C)O)R) 1 coding Cadherin-20 precursor. ENST00000324774 NP_757363 (((H,G)C)O)R) 1 coding Calcium/calmodulin-dependent protein kinase kinase 2 ENST00000308191 NP_061818 (((H,G)C)O)R) 1 coding cAMP-specific 3' ENST00000256119 NP_001729 (((H,G)C)O)R) 1 coding Carbonic anhydrase 1 ENST00000375908 NP_666023 (((C,G)H)O)R) 1 coding Cathepsin L precursor ENST00000322773 NP_001849 (((C,G)H)O)R) 1 coding Collagen alpha-1(XIX) chain precursor ENST00000297135 NP_006339 (((H,G)C)O)R) 1 coding Conserved oligomeric Golgi complex component 5 ENST00000377327 NP_057736 (((H,G)C)O)R) 1 coding Crooked neck-like protein 1 ENST00000241312 NP_443128 (((H,G)C)O)R) 1 coding CUB and sushi domain- containing protein 2 ENST00000241312 NP_443128 (((C,G)H)O)R) 1 coding CUB and sushi domain- containing protein 2 ENST00000275016 NP_057677 (((C,G)H)O)R) 1 coding Cytochrome P450 39A1 ENST00000367089 NP_006510 (((C,G)H)O)R) 1 coding Cytoplasmic dynein light chain (T-complex testis-specific protein 1 homolog) ENST00000351513 NP_001376 (((C,G)H)O)R) 1 coding Dihydropyrimidinase ENST00000367749 NP_002013 (((C,G)H)O)R) 1 coding Dimethylaniline monooxygenase ENST00000340748 NP_001370 (((C,G)H)O)R) 1 coding DNA (cytosine-5)- methyltransferase 1 ENST00000255078 NP_002171 (((H,G)C)O)R) 1 coding DNA-binding protein SMUBP- 2 ENST00000261769 NP_004351 (((C,G)H)O)R) 1 coding Epithelial-cadherin precursor ENST00000274024 NP_000125 (((H,G)C)O)R) 1 coding Fatty acid-binding protein ENST00000323936 NP_001008728 (((C,G)H)O)R) 1 coding HMG2 like isoform 1 ENST00000331817 NP_005547 (((C,G)H)O)R) 1 coding Keratin ENST00000361841 NP_588608 (((H,G)C)O)R) 1 coding Membrane progestin receptor beta ENST00000302326 NP_002421 (((C,G)H)O)R) 1 coding meningioma (disrupted in balanced translocation) 1 ENST00000305432 NP_000833 (((C,G)H)O)R) 1 coding Metabotropic glutamate receptor 5 precursor ENST00000310776 NP_064576 (((H,G)C)O)R) 1 coding Mitochondrial 28S ribosomal protein ENST00000347778 NP_038479 (((C,G)H)O)R) 1 coding Myoferlin ENST00000316877 NP_056273 (((C,G)H)O)R) 1 coding Myotubularin-related protein 9 ENST00000320704 NP_001001968 (((H,G)C)O)R) 1 coding Olfactory receptor 6S1 ENST00000374463 (((H,G)C)O)R) 1 coding OTTHUMP00000021898 (CCP module-containing protein).
  • 45. 45 ENST00000304979 NP_006338 (((C,G)H)O)R) 1 coding Peptidyl-prolyl cis-trans isomerase H ENST00000295887 NP_001254 (((H,G)C)O)R) 1 coding Phosphatidate cytidylyltransferase 1 ENST00000351298 NP_002653 (((H,G)C)O)R) 1 coding Phospholipase D1 ENST00000299796 NP_950251 (((C,G)H)O)R) 1 coding Protein C21orf25 precursor ENST00000361432 NP_996892 (((H,G)C)O)R) 1 coding Protein FAM45A ENST00000333538 NP_071924 (((C,G)H)O)R) 1 coding Putative polypeptide N- acetylgalactosaminyltransferase- like protein 3 ENST00000381588 NP_898864 (((H,G)C)O)R) 1 UTR RING finger protein 6 ENST00000265882 NP_057174 (((H,G)C)O)R) 1 coding RNA-binding protein 7 ENST00000306698 NP_612493 (((C,G)H)O)R) 1 coding Shugoshin-like 1 (hSgo1) (Serologically defined breast cancer antigen NY-BR-85). ENST00000369503 NP_060890 (((C,G)H)O)R) 1 coding solute carrier family 22 ENST00000299233 NP_666018 (((H,G)C)O)R) 1 coding solute carrier family 5 ENST00000307378 NP_066580 (((H,G)C)O)R) 1 coding Solute carrier organic anion transporter family member 1A2 ENST00000258381 NP_536349 (((H,G)C)O)R) 1 coding Sp110 nuclear body protein (Speckled 110 kDa) ENST00000295798 NP_003117 (((H,G)C)O)R) 1 coding Spectrin alpha chain ENST00000262715 NP_009041 (((H,G)C)O)R) 1 coding Telomerase protein component 1 ENST00000313105 NP_665802 (((C,G)H)O)R) 1 coding TNF receptor-associated factor 6 ENST00000338560 NP_057197 (((C,G)H)O)R) 1 coding Transient receptor potential cation channel subfamily V member 2 ENST00000251272 NP_006291 (((H,G)C)O)R) 1 coding Zinc finger protein 230 ENST00000361959 NP_597733 (((C,G)H)O)R) 1 coding Zinc finger protein 384 (Nuclear matrix transcription factor 4) ENST00000314393 NP_055758 (((C,G)H)O)R) 1 UTR Zinc fingers and homeoboxes protein 2 ENST00000314393 NP_055758 (((C,G)H)O)R) 1 coding Zinc fingers and homeoboxes protein 2 ENST00000343833 NP_659419 (((C,G)H)O)R) 1 coding Proline/Serine-rich coiled-coil 2 ENST00000310850 NP_542395 (((H,G)C)O)R) 1 coding hypothetical protein LOC112487 ENST00000245957 NP_056400 (((H,G)C)O)R) 1 coding hypothetical protein LOC26074 ENST00000160713 NP_056996 (((H,G)C)O)R) 1 coding hypothetical protein LOC51059 ENST00000314400 NP_056227 (((C,G)H)O)R) 1 coding hypothetical protein LOC25871 isoform a ENST00000251691 NP_065073 (((C,G)H)O)R) 1 coding hypothetical protein LOC57221 ENST00000313159 (((C,G)H)O)R) 1 coding ENST00000355150 NP_056308 (((C,G)H)O)R) 0,99 coding ankyrin repeat domain 25 ENST00000342358 NP_940907 (((H,G)C)O)R) 0,99 coding ATPase type 13A5 ENST00000256119 NP_001729 (((C,G)H)O)R) 0,99 coding Carbonic anhydrase 1(CA-I). ENST00000282358 NP_848018 (((H,G)C)O)R) 0,99 coding Coiled-coil domain-containing protein 50 ENST00000337623 NP_056423 (((H,G)C)O)R) 0,99 coding erythroid differentiation-related factor 1 ENST00000248098 NP_653171 (((H,G)C)O)R) 0,99 coding Hematological and neurological expressed 1-like protein ENST00000307851 NP_116171 (((C,G)H)O)R) 0,99 coding Hepatitis A virus cellular receptor 2 precursor ENST00000355057 NP_003536 (((C,G)H)O)R) 0,99 coding Histone H4 ENST00000263087 NP_002199 (((C,G)H)O)R) 0,99 coding Integrin alpha-E precursor
  • 46. 46 ENST00000272000 NP_001005736 (((C,G)H)O)R) 0,99 coding Lysosomal trafficking regulator ENST00000339200 NP_003675 (((H,G)C)O)R) 0,99 coding MAP kinase-interacting serine/threonine-protein kinase 1 ENST00000340694 (((H,G)C)O)R) 0,99 coding Neurabin-1 (Neural tissue- specific F-actin binding protein I) ENST00000360409 NP_957716 (((C,G)H)O)R) 0,99 coding Neuropilin-2 precursor ENST00000369682 NP_059984 (((C,G)H)O)R) 0,99 coding Plexin-A3 precursor (Plexin-4) ENST00000262477 NP_004694 (((H,G)C)O)R) 0,99 coding Rab GTPase-binding effector protein 1 ENST00000237305 NP_005618 (((C,G)H)O)R) 0,99 coding Serine/threonine-protein kinase Sgk1 ENST00000360456 NP_066287 (((H,G)C)O)R) 0,99 coding Sodium channel protein type 2 alpha subunit ENST00000284322 NP_056244 (((C,G)H)O)R) 0,99 coding Target of Nesh-SH3 precursor ENST00000281523 NP_078973 (((C,G)H)O)R) 0,99 coding Zinc finger protein 659 ENST00000309050 NP_997318 (((H,G)C)O)R) 0,99 coding hypothetical protein LOC400073 ENST00000193403 NP_001093 (((H,G)C)O)R) 0,98 coding Alpha-actinin-1 ENST00000237612 NP_004818 (((C,G)H)O)R) 0,98 coding ATP-binding cassette sub- family G member 2 (Breast cancer resistance protein) ENST00000360606 NP_065928 (((C,G)H)O)R) 0,98 coding dynein heavy chain domain 3 ENST00000324138 NP_001018123 (((C,G)H)O)R) 0,98 coding Fanconi anemia group B protein ENST00000261887 NP_003913 (((H,G)C)O)R) 0,98 coding guanine nucleotide exchange factor p532 ENST00000380206 NP_000596 (((H,G)C)O)R) 0,98 coding Interferon alpha-2 precursor ENST00000328496 NP_001010891 (((H,G)C)O)R) 0,98 coding metaxin 3 ENST00000341919 NP_005588 (((H,G)C)O)R) 0,98 coding Nuclear factor 1 C-type ENST00000228495 NP_114160 (((C,G)H)O)R) 0,98 coding potassium channel tetramerisation domain containing 10 ENST00000298925 NP_006148 (((H,G)C)O)R) 0,98 coding Protein kinase C-binding protein NELL1 precursor ENST00000336735 NP_005056 (((C,G)H)O)R) 0,98 coding Sel-1 homolog precursor ENST00000286827 NP_003244 (((H,G)C)O)R) 0,98 coding T-lymphoma invasion and metastasis-inducing protein 1 ENST00000236709 NP_057245 (((C,G)H)O)R) 0,97 coding Alpha-1,4-N- acetylglucosaminyltransferase ENST00000325551 NP_003789 (((H,G)C)O)R) 0,97 coding Alpha-catulin ENST00000376427 NP_777598 (((C,G)H)O)R) 0,97 coding FERM domain containing 3 ENST00000230990 NP_001936 (((H,G)C)O)R) 0,97 coding Heparin-binding EGF-like growth factor precursor ENST00000328939 NP_055407 (((H,G)C)O)R) 0,97 coding Kv channel-interacting protein 1 ENST00000341893 NP_078824 (((C,G)H)O)R) 0,97 coding leucine-rich repeats and IQ motif containing 2 ENST00000361649 NP_000433 (((H,G)C)O)R) 0,97 coding Platelet endothelial cell adhesion molecule precursor ENST00000302078 NP_002660 (((C,G)H)O)R) 0,97 coding Pleiotropic regulator 1 ENST00000366769 NP_003598 (((C,G)H)O)R) 0,97 coding Serine/threonine-protein kinase MRCK alpha ENST00000278616 NP_000042 (((H,G)C)O)R) 0,97 coding Serine-protein kinase ATM ENST00000322940 NP_060302 (((H,G)C)O)R) 0,97 coding hypothetical protein LOC54942 ENST00000335012 NP_001020437 (((C,G)H)O)R) 0,97 coding hypothetical protein LOC285382 ENST00000261842 NP_031373 (((C,G)H)O)R) 0,96 coding AP-4 complex subunit epsilon-1 ENST00000346717 NP_005010 (((C,G)H)O)R) 0,96 coding Calcium/calmodulin-dependent
  • 47. 47 3' ENST00000375908 NP_666023 (((C,G)H)O)R) 0,96 coding Cathepsin L precursor ENST00000262625 NP_954649 (((H,G)C)O)R) 0,96 coding Kin of IRRE-like protein 2 precursor ENST00000381482 NP_543026 (((H,G)C)O)R) 0,96 coding Serine/threonine-protein kinase 35 ENST00000375451 NP_848561 (((H,G)C)O)R) 0,96 coding Short palate ENST00000271359 NP_000687 (((C,G)H)O)R) 0,95 coding 4-trimethylaminobutyraldehyde dehydrogenase ENST00000367492 NP_114141 (((C,G)H)O)R) 0,95 coding Hemicentin-1 precursor (Fibulin-6) ENST00000302085 NP_005891 (((C,G)H)O)R) 0,95 coding Mothers against decapentaplegic homolog 1 (SMAD 1) ENST00000226207 NP_005954 (((H,G)C)O)R) 0,95 coding Myosin-1 ENST00000313478 NP_060142 (((H,G)C)O)R) 0,95 coding Transient receptor potential cation channel subfamily M member 7 ENST00000372771 NP_036553 (((H,G)C)O)R) 0,95 coding Zinc finger protein Rlf ENST00000262996 NP_055945 (((H,G)C)O)R) 0,95 coding TBC1 domain family, member 9
  • 48. 48 Supplementary Table 2 Apomorphic morphological characters in support of varying human-chimpanzee-gorilla phylogenies Character Status ID (H,C) Honing in males Further reduced 48 Pelvis: obturator groove deep/well defined 70 Premaxillary suture Obliterated in adult 130 Ankle epiphysis Not delayed relative to elbow 154 Geniohyoideus insertion above inferior transverse torus 186 Insertion of Digastric Inferior transverse torus 187 Ileo-caecal valve Widened 210 Cranial end of heart Shifted upward 215 Puberty Reached at >7 years 224 Axis of earbones Acute angle 103 Encephalization High (>11) 220 Penis (erected) Lengthened (>80 mm) 235 (H,G) Talus (Astragalus) Widened 146 Rectum flexure Present 199 Hair density on scalp Reduced 254 Hair density on chest Very sparse 256 Angle of Manubrium Mallei >45° 105 Ovaries Very large (>40 mm long) 230 Fluorescent F body Present 239
  • 49. 49 Ear breadth <75% of height 246 (C,G) Metacarpal heads Expanded 140 Oestrus swelling in females Reduced 241 Metaconid of dP3 Absent 167 Metaconid of dP4 Increased relative to protoconid on dP4 170 Christa oblique on dP4 Does not reach protoconid apex 171 Talonid basin on dP4 Open distally 172 Pattern 3 enamel Proportion very reduced 179 Index of Palaeocortex Relatively enlarged (0.5-0.8) 221 Ethmoid-lacrymal contact Shortened (40-90%) A69 Fronot-maxillary contact in Contact (30-50%) A70 orbits (H,C), (H,G) and (C,G) identify the two species exclusively sharing the apomorphic character state. Characters and the apomorphic character state are briefly described in the corresponding columns. Column ‘ID’ gives the character identifier used in the original publications (48-256: Shoshani et al. 1996; A69 and A70: Collar and Wood 2000).
  • 50. 50 Supplementary Figure 1
  • 51. 51 Supplementary Figure 2

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