Exploration about the Evolution of Human Limb Diaphyseal Structure in Pleistocene Eurasia

1. Exploration about the Evolution of Human Limb
Diaphyseal Structure in Pleistocene Eurasia
Yuhao Zhao, Pianpian Wei, Song Xing

2. 1. Morpho-functional studies of human limbs can provide key information on the locomotor patterns, habitual behaviors, and subsistence
strategies of past populations.
2. In comparison to the well-studied limb fossils from Pleistocene to Holocene Europe, limb remains from East Asia are rare, and the
evolutionary process of human limbs in this region has not been sufficiently investigated.
3. Present understanding of the overall evolutionary pattern of human limb structure and function is mainly built on linear measurements
and cross-sectional geometric (CSG) properties at limited cross-sections, which are insufficient to reveal the full information hidden
beneath the limb diaphysis.
Backgrounds
Objectives
To reveal the morphological and functional patterns across complete humeral and femoral diaphysis of East Asian early modern humans,
European early modern humans, Neandertahls, and Homo erectus from Pleistocene and to Early Holocene.

3. Materials Humeral samples
Tianyuan 1 Zhaoguo M1 Qihe M2 Regourdou 1
Age-at-death 40-60 ~40 ~30 23-30
Sex male male Female male
Stature (cm) 169.0-177.0 -- 160.3 166.4
Body mass (kg) 85.0 -- 59.9 65.6
Estimated handedness right-handed Left-handed -- Right-handed
Data/time period 42,000-39,000 cal BP 11,068-10663 cal BP 8,428-8,359 cal BP Marine Isotope Stage (MIS) 4
Location
Zhoukoudian, Beijing,
North China
Pingba district, Guizhou
Province, South China
Zhangping city, Fujian Province,
South China
near the site of Lascaux,
Dordogne, France
Estimated biomechanical length (mm) 327.4 313.9 277.5 303.8
Early Modern Human Neanderthal Homo erectus
East Asia Europe
BD5 CDV-Tour 1 Kresna 11
Site
Tianyuan Cave
(TYD)
Maomao Cave
(MMD)
Liujiang (LJ) Chancelade 1
Location
Zhoukoudian, Beijing,
North China
Dingxiao, Xingyi, guizhou
Liujiang, Liuzhou,
Guangxi
Dordogne,
Southwestern France
Charente,
Southwestern
France
Charente,
Southwestern
France
Sangiran Dome,
Central Java,
Indonesia
Date/Time
period
42,000-39,000 cal BP ~14,600±1,200 cal BP MIS 2 18,031-18,480 cal BP MIS 5e MIS 3 0.9-1.5 Ma BP
Femoral samples

4. Methods Morphometric map
Morphometric map is a virtual 2D colormap rendering
by a chromatic scale of colors increasing from dark
blue (minimum value) to bright red (maximum value).
A: 100 cross-sections along the proximodistal limb
diaphysis were virtually extracted at equi-distance.
B: 360 equi-angular landmarks were placed along the
internal (endosteum) and external (periosteum)
contours at every cross-section.
C: Cortical bone thickness (CBT) was calculated as
the distance between the external and internal
landmarks.
D: External radius (ER) was calculated as the
distance between the external landmarks and the
centroid of the internal surface.
E: Second moment of area (SMA) was utilized to
indicate the bending rigidity for each direction.
ant: anterior
lat: lateral
med: medial
post: posterior
prox: proximal
mid: middle
dist: distal

5. Methods The distribution of CSG properties across the entire limb diaphysis
J Ix/Iy
Polar second moment of area (J) is
utilized to indicate the torsional or
average bending rigidity of a cross-
section.
biomechanical shape ratio (Ix/Iy) is
calculated as the ratio of the second
moment of area about mediolateral (x)
axis to the second moment of area
about anteroposterior (y) axis, which is
equivalent to the ratio of A‐P bending
rigidity to M-L bending rigidity.

6. Tianyuan 1 L Tianyuan 1 R Zhaoguo M1 L Zhaoguo M1 R
Qihe M2 L Qihe M2 R
0.56
4.02
Regourdou 1 R
Results
Humeral morphometric maps
for cortical bone thickness
 CBT distribution pattern was similar among
all specimens: All specimens exhibited the
thinnest cortex in the proximal shaft and
thickest cortex in the lateral aspect of the
distal shaft. All specimens showed anterior
cortical reinforcement along the proximo-
distal diaphysis, medial reinforcement from
the middle (~50%) to distal (20%)
diaphysis, and posterior reinforcement mid-
distally (~50%-~35%).
 The magnitude of cortical thickness for the
right Regourdou 1 humerus was greater
than that of other humeri. For East Asian
specimens, Zhaoguo M1 humeri were
thicker than that of Tianyuan 1 and Qihe
M2.

7. 2.03
4.69
Tianyuan 1 L Tianyuan 1 R Zhaoguo M1 L Zhaoguo M1 R
Qihe M2 L Qihe M2 R Regourdou 1 R
Results
Humeral morphometric maps
for external radius
 All humeri showed similar ER distribution
patterns with posterior, medial and anterior
enlargement proximally, anterolateral and
medial enlargement mid-proximally, posterior,
medial, and anterior enlargement mid-distally,
and lateral enlargement distally.
 The ER values of the Regourdou 1 right
humerus was larger than that of other
specimens within the medial, anterior and
lateral aspects, and the Tianyuan 1 left
humerus exhibited the minimum ER globally.
 The ER magnitude of Qihe M2 humeri was
slightly greater than that of Tianyuan 1 right
and Zhaoguo M1 humeri, especially along the
medial and lateral aspects.

8. 1.41
9.86
Tianyuan 1 L Tianyuan 1 R Zhaoguo M1 L Zhaoguo M1 R
Qihe M2 L Qihe M2 R Regourdou 1 R
Results
Humeral morphometric maps
for bending rigidity
 The Tianyuan 1 humeri exhibited the
maximal sSMA along the posteromedial-
anterolateral axis around the region of
midshaft.
 Both of Zhaoguo M1 humeri and
Regourdou 1 right humerus exhibited the
maximal sSMA along the posteromedial-
anterolateral axis most-proximally,.
 the region of enhanced sSMA for Qihe
M2 humeri was at the proximal-most
section and from the mid-proximal to
middle diaphysis.
 The sSMA values of Regourdou 1 right
humerus was larger than any of the other
humeri in the sample.

9. Results
Humeral morphometric maps for absolute asymmetry
(%AA) of cortical bone thickness, bending rigidity, and
external radius
 The CBT %AA of Tianyuan 1 humeri were slightly higher than the Zhaoguo
M1 and Qihe M2 humeri.
 The SMA %AA of Tianyuan 1 humeri was considerably higher when
compared to Zhaoguo M1 and Qihe M2.
 The distribution pattern of SMA %AA differed by specimen. The reinforced
regions of SMA %AA in Zhaoguo M1 humeri were along the medial-lateral
axis distally. The reinforced regions of Tianyuan 1 SMA %AA exhibited all
compartments along the proximodistal diaphysis except the proximal-most
medial-lateral axis and the mid-proximal anterior-posterior axis. The Qihe
M2 SMA %AA was reinforced along the posterolateral-anteromedial axis
mid-proximally.
 Unlike the relatively high ER %AA of Tianyuan 1 humeri, there were almost
no ER %AA for Zhaoguo M1 and Qihe M2 humeri.

10. Results
 sJ generally increased from the distal to proximal diaphysis.
 The sJ of Regourdou 1 right humerus was significantly larger than that of other
specimens, and the Tianyuan 1 left humerus exhibited the smallest sJ.
 The sJ of Tianyuan 1 right humerus was obviously larger than that of the left one.
 The sJ values of Zhaoguo M1 right and left humeri was very close, with the left
humerus sJ slightly larger.
 The sJ value of Qihe M2 right humerus was slightly larger than that of the left one
along the proximo-distal diaphysis.
 The J %AA of Tianyuan 1 humeri was obviously larger than that of Zhaoguo M1 and
Qihe M2.
 Qihe M2 J was larger than Zhaoguo M1 from mid-proximal to middle diaphysis.
Humeral continuous torsional rigidity distribution

11. Results
Femoral morphometric maps
for cortical bone thickness
 For neandertal specimens (BD5 and CDV-Tour 1), high
CBT values distributed laterally across the proximal to
middle diaphysis, with a narrow thicker region
distributed posteriorly along the shaft (indicating a less
developed linea aspera).
 Thick cortex of Indonesian Homo erectus (Kresna 11)
distributed medially across the proximal to middle
diaphysis, posteriorly across the proximal to mid-distal
diaphysis, and laterally across the proximal to mid-
proximal diaphysis.
 European (Chancelade 1) and East Asian (TYD, MMD,
LJ) EMHs had similar distribution pattern: Thick cortex
distributed posteriorly across the mid-prximal to mid-
distal diaphysis (indicating a developed pilaster).

12. Results
Femoral morphometric maps
for external radius
 For neandertal specimens (BD5 and CDV-Tour 1), high
ER values distributed laterally across the proximal to
mid-proximal diaphysis, with a narrow thicker region
distributed posteriorly along the shaft.
 Enlarged ER of Indonesian Homo erectus (Kresna 11)
distributed laterally across the proximal to mid-proximal
diaphysis.
 East Asian EMHs (TYD, MMD, LJ) had similar
distribution pattern: higher ER values distributed
posteriorly across the middle to mid-distal diaphysis.
 Higher ER values of European EMHs (Chancelade 1)
distributed anteromedially and posterolaterally at the
distal diaphysis.

13. Femoral morphometric maps
for bending rigidity
Results
 For neandertal specimens (BD5 and CDV-Tour 1) and
Indonesian Homo erectus (Kresna 11), SMA values
distributed mediolaterally across the mid-proximal to
mid-distal diaphysis.
 For European (Chancelade 1) and East Asian (TYD,
MMD, LJ) EMHs, SMA values distributed mediolaterally
across the mid-proximal to mid-distal diaphysis.

14. Results
Distribution of continuous biomechanical shape ratio
across the femoral diaphysis
The Ix/Iy ratios indicated that the femora of all East
Asian and European EMHs had greater A-P than M-L
bending rigidity across the mid-proximal to mid-distal
diaphysis, while Neanderthals and Homo erectus had
greater M-L than A-P bending rigidity along the entire
femoral shaft.

15. Brief Conclusions
 the femora of EMHs from East Asia and Europe shared similar
distribution patterns of CBT, ER, SMA, and Ix/Iy, which were distinct
from Neanderthals and Indonesian Homo erectus.
 Between EMHs from North and South China and Neanderthals, the
CBT, ER, and J had similar distribution patterns but differed in the
overall magnitude along the humeral diaphysis, and the SMA layouts
were various.

16. Yuhao Zhao zhaoyuhao@ivpp.ac.cn
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese
Academy of Sciences, Beijing 100044, China
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Pianpian Wei
Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Anthropology and Human Genetics, School of Life
Sciences, Fudan University, Shanghai 200433, China
Song Xing xingsong@ivpp.ac.cn
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese
Academy of Sciences, Beijing 100044, China