Many large mammals from woolly mammoths to saber-tooth tigers went extinct around 10,000 years ago during the last great Ice Age. Though external factors such as ancient human hunting, climate change, and even asteroid impacts have been speculated, the determining forces driving massive extinction remains elusive. Recent analyses on abundant genomic data suggest that elevated genetic mutations can cause extinction. In this study, we took advantage of the recently available and well-preserved mitochondrial DNAs from extinct mammals to identify genetic mechanisms driving the extinction of megafauna. We compared substitution patterns between 25 extinct animals and their living relatives. This was accomplished through the use of the bioinformatic software Geneious Prime and phylogenetic trees. Overall, extinct mammals show more C -> T and A -> G substitutions on the light strand, but fewer G -> A and T -> C substitutions than their living relatives in the Cytochrome C Oxidase, Cytochrome B, ATP Synthase complexes, and NADH Dehydrogenase. This suggests subtle differences in DNA replication and/or repair between the extinct lineages and living relatives. The overall dN/dS ratio was significantly higher in the extinct animals compared to their living relatives, indicating prolonged small population sizes. Our study sheds light on the understanding of mechanistic factors in massive extinction and will help generate knowledge to prevent future extinctions.

1. Jacob Kostecke
&
Weilong Hao

2. The Pleistocene Era
• 2.5 million to 10,000 years ago
• Last great ice age
• Mega mammals
• Woolly Mammoths &
Rhinos
• Giant Sloths & Bears
• Saber Tooth Tigers

3. Knowledge Gap
• The current research is insubstantial
• Humans?
• Climate Change?
• Asteroid?
• Genetic mutations?
• Why Genetic Mutations?
• More mutations can lead to extinction
• Unique perspective

4. The Hypothesis “I hypothesize that accelerated genetic mutation
plays a major role in the extinction of mega
mammals during the Pleistocene era”

5. Aims 1
“Aim 1 will determine whether the
extinct mammals have undergone
accelerated evolution compared to
their closest relatives”
• If an extinct species were under
accelerated evolution than all
genomic region have high
substitution rates.
• Longer branches are a proxy for more
mutation accumulation
• Extinction branch should be shorter
compared to living due to dying out earlier

6. ”Aim 2 will determine whether all extinct species
suffered a prolonged small population size”
Aims 2
High dN/dS ratio
Low dN/dS ratio
• Compare synonymous vs
nonsynonymous substitutions
between extinct and living species
• Ratio = nonsynonymous over
synonymous substitution rates
(dN/dS ratio)
• Higher dN/dS ratio indicates more
relaxed selection
• Determine how much accelerated
evolution is cause by
nonsynonymous substitution
Population sizes

7. • 25 extinct mammal species
• 13 coding genes each
• BLAST to find 3 closest living relatives
• Constructed Phylogenetic trees to see relationship
• Alignment of extinct with 1st & 3rd living relatives
(outgroup)
• Mitochondrial Genomes are an Excellent Vessel
• Abundant in preserved specimen
• Well preserved & smaller size
• Traceable mutation patterns easily interpreted
The Methods

8. Results: Synonymous
Substitutions
• The Data
• Greater substitutions in extinct
lineages
• Extinct lineages have different
mutations patterns than living
relatives
• These are also supported in analyses
on non-synonymous subs and in
different functional complexes
• Conclusion
• Extinct underwent accelerated
mutation accumulation before
dying out
* Check out the Data Tab to see the break down of mutations per genes

9. Results: dN/dS Ratio
• dN/dS Ratio
• The higher dN/dS ratio is
consistent with more relaxed
selection due to prolonged small
population size
* Check out the Data Tab to see the break down of ratios per genes
• The Data
• Extinct species had higher dN/dS
Ratio of mutations than living
• Extinct had more nonsynonymous
mutations
• Conclusion
• Extinct species underwent
accelerated evolution under a
prolonged small population before
dying out
# non-syn # syn Ratio
Extinct 1319 7267 0.182
Living 1128 6722 0.168
Chi-square P-Value 0.000

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