Hominins and Hominids

Everyone is interested in their ancestors, some people are just interested much further back than others. A recent paper in Nature describes the characterization of the most complete skull fossil ever found for Australopithecus anamensisAnamensis is one of the 5 species of Australopithecus, the genus that is believed to have given rise to Homo sapiens, i.e. modern humans. The group consisting of Australopithecus, modern humans, extinct human species, and all our immediate ancestors is known as the Hominins. Hominins are part of a larger group called Hominids that also includes some of the great apes that are not directly in our ancestral lineage. Unraveling the evolutionary relationships between the members of these groups is challenging, but progress continues to be made. Now having a nearly complete skull allows much more precise facial reconstruction which gives us a vivid glimpse of what this forebear may have looked like. Interestingly, the reconstruction shows evidence for both ancient and more modern facial features.

Dating of the skull’s age also establishes that A. anamensis existed longer than previously thought and likely lived concurrently with the next lineage, A. afarensis, for around 100,000 years. The probable co-existence of these two Australopithecus species supports the conclusion that their evolution was not a straightforward, linear progression. Instead, these two species could have interacted and even interbred for millennia, making the direct ancestor of Homo genus even less clear.

Looking at more recent history, there are several fascinating reports giving new insight into our close relative, Homo neanderthalensis. It is now well established that the two Homo species of sapiens and neanderthalensis did interbreed, with modern humans of European descent carrying around 2% of Neanderthal DNA in our genomes.  These inherited genes still matter as there is evidence that some retained Neanderthal DNA affects both our cranium shape and brain development. Another report late last year suggests that part of the selective pressure keeping some other segments of Neanderthal DNA in our genomes was driven by protection conferred to viruses that were likely shared between the two species. As an example of virus sharing, modern humans appear to have acquired genital human papillomaviruses via sexual transmission from Neanderthals. Yes, among other things our ancestors gave us an STD! Molecular and genetic analysis makes it clearer and clearer that both genes and infectious diseases are strongly influenced by our ancestral history. We may think of ourselves as vastly superior to our predecessors, but we can’t escape our evolutionary heritage and the impact it still exerts on our biology and health.

I hope you enjoyed this brief look at our ancient relatives, and if you did, remember to “like” the site and tell your friends. Also, if there are scientific topics you would like to hear about just send me suggestions.

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