Recently we have uncovered that epigenetic changes are able to be passed on to our offspring. If this is the case, how long has this been occurring? In fact, epigenetic changes in DNA occur in our ape relatives as well. But is human epigenetic modification different than apes?
Scientists recently have been investigating this question and revealed revolutionary findings. In 2012 Shulha et al sought through the field of epigenetics to learn more about what makes us uniquely human. The group studied a particular histone modification within the DNA of a human, chimpanzee, and macaque prefrontal cortex. (Frontal cortex of various species highlighted in image below). The results showed, "471 sequences with human-specific enrichment or depletion" (Shulha et al, 2012). Therefore nearly 500 gene sequences are specific to humans rather than chimpanzee or macaque for epigenetic modification. This step demonstrates that perhaps an additional factor into the differences in behavior between humans and our relatives are epigenetic changes specific to our species. 
Another study published in 2012 investigates a similar concept. Zeng et al looked to further understand how DNA methylation patterns differed between species and how these differences affected particular traits. The research is similar to Shulha et al in that these scientists also looked at the prefrontal cortex of chimpanzees and humans. By creating, "nucleotide-resolution whole-genome methylation maps," (Zeng et al, 2012), researchers were able to determine that human brains contained hundreds of genes which had lower levels of promoter methylation than chimpanzees. These lower levels were found to also be present in next generation and effect gene expression. As the researchers proclaimed, "Our results demonstrate that differential DNA methylation might be an important molecular mechanism driving gene-expression divergence between human and chimpanzee brains and might potentially contribute to the evolution of disease vulnerabilities. Thus, comparative studies of humans and chimpanzees stand to identify key epigenomic modifications underlying the evolution of human-specific traits." (Zeng et al, 2012).
Both studies demonstrate the importance of understanding epigenetics because it clearly could play an important role in evolution and thus human behavior. The research helps us learn more about the differences between humans and our ancestors, and provides a stepping stone for future research. Evolution and epigenetics are closely related and can both explain much about human behavior.
References:
Shulha HP, Crisci JL, Reshetov D, Tushir JS, Cheung I, et al. (2012) Human-Specific Histone Methylation Signatures at Transcription Start Sites in Prefrontal Neurons. PLoS Biol 10(11): e1001427. doi:10.1371/journal.pbio.1001427
Zeng, J., Konopka, G., Hunt, B. G., Preuss, T. M., Geschwind, D., & Yi, S. V. (2012). Divergent Whole-Genome Methylation Maps of Human and Chimpanzee Brains Reveal Epigenetic Basis of Human Regulatory Evolution. American Journal of Human Genetics, 91(3), 455–465. doi:10.1016/j.ajhg.2012.07.024
Pictures all accessed 12/04/2015 and referenced from top to bottom of blog entry:
http://theadvancedapes.com/wp-content/uploads/2013/06/cadelllast_24677585214750_small.jpg
http://blogs.scientificamerican.com/beautiful-minds/files/2013/05/Semendeferi-Damasio1-300x216.png
http://www.redorbit.com/media/uploads/2013/02/humanchimp.jpg
http://zenbullets.com/blog/images/bigbrains.gif
A fascinating post. You say that humans have lower levels of promoter methylation than chimps … does this mean that chimp phenotypes are more dynamic and flexible, able to change more rapidly than humans? I would have thought we’d have more than 500 genes specific to humans, considering our complexity in social structure, our language and our cultural ability (i.e. music and the arts). What is your opinion – is this a large variation, or a relatively small one?
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