Go back a hundred thousand years, 4,000 generations, and things were different. You’d need about 10 photo albums or a couple hundred screens of thumbnails to hold a snapshot of just one person in each generation back that far. What would your ancestor from then look like? For one thing, he or perhaps more likely she might be a Neanderthal.
Biologically, humans today belong to one race. Back then, however, there were two. One was us, and the other was the Neanderthals. (See http://news.softpedia.com/newsImage/Humans-and-Neand.….#45;2.jpg/ for reconstructed image of Neanderthal child.) Heavier, stronger, and with larger brains than ours, intermarriage or at least interbreeding between these two races of humans occurred, leading to a small but significant fraction of the average non-African person’s genome being Neanderthal. Physical features of Neanderthals often considered “distinguishing” can in fact be found in some people. For example some people have an occipital bun — a bump or protrusion on the back of the head. Other people might have particularly heavy brow ridges, or thick, bowed thigh bones, or a barrel-shaped rib cage, and so on.
The photo from 100,000 years ago in your collection might indeed be a Neanderthal, however, more likely it would not be. What would it look like, then? It wouldn’t be a Flores Man (Homo floresiensis), the 3 – 4 foot tall hobbit-like species whose bones have been found on Flores Island, Indonesia. Apparently more closely related to humans than any other species, these short, hobbit-like hominids (if one hesitates to call them people, “animal” induces hesitation as well) survived at least until 12,000 years ago and just maybe almost into modernity, possibly giving rise to the Floresian Ebu Gogo (“grandmother who eats everything”) legend. Perhaps Flores Man still exists, living unnoticed in jungles of the region.
If this picture from a hundred thousand years ago was not a Neanderthal, then what was it? Except for the Neanderthal race, humans had not yet left Africa. Hence doubtless they had not yet developed the light skin color adaptation that enables better vitamin D production in the diminished sunlight intensity of higher latitudes (at the price of increased susceptibility to sunburn and skin cancer). For the same reason, today’s modest regional variations in facial features had not yet developed, nor had any other present-day regional genetically based variations, from visible and known (green eyes, etc.), to unknown and waiting to be discovered in the future.
100,000 years ago we were different, but hardly unrecognizably so. Thus, it is likely that 100,000 years from now we will also look different — yet still clearly human. At 4,000 generations, that many years is enough for even very slight selective pressures to cause significant evolutionary changes to the human species. Today’s regional variations in appearance (facial features, stature, skind color), which did not exist 100,000 years ago, will be long since lost in the mists of history. If we can identify existing evolutionary pressures and extrapolate, thus envisioning their magnified effects, that might help characterize humanity as it moves forward toward 100,000 year from now. If the brain is our essence, that essence will change. But how? Here is just one example (science should identify as many others as possible).
Do you think a gene for high ability to distinguish between fantasy and reality will tend to propagate to the next generation more successfully than poor such ability? I am not so sure, but suppose for a moment it will. Now consider a part of the brain that correlates with and likely confers just such an ability: the paracingulate sulcus (PCS). Some people have two well-developed PCSs (one in the left hemisphere and one in the right). Some have just one. Others none. PCSs can be well-developed, missing, or anything in between. It might not be long before an eye witness in a high-stakes criminal court case will have the size and number of her paracingulate sulci splashed across news screens world wide. Dating services will soon have decide: are people with similar PCSs more compatible, or is this a case where opposites attract? It is suggested that of two individuals with the same degree of schizophrenia-induced hallucinations, the one with better PCSs will likely handle it better and be more able to function. (It is unknown if Nobel prize-winning economist and schizophrenia sufferer John Nash has good PCSs or not. Einstein’s brain, however, is in storage and could be checked.) Chimpanzees do not have paracingulate sulci. If good paracingulate sulci, on balance, benefit reproduction, in 100,000 years most everyone will have good ones. If the opposite — no one will!
References
“Apparently more closely related to humans than any other species, these small hominids…survived until at least as recently as 12,000 years ago…”: M. J. Morwood, P. Brown, Jatmiko, T. Sutikna, E. W. Saptomo, K. E. Westaway, R. A. Due, R. G. Roberts, T. Maeda, S. Wasisto, and T. Djubiantono, Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia, Nature, Oct. 13, 2005, vol. 437, no. 7061, pp. 1012 – 1017.
Http://www.ncbi.nlm.nih.gov/pubmed?term=16229067.
“Now consider a part of the brain that confers just such an ability: the paracingulate sulcus (PCS).” M. Buda, A. Fornito, Z. M. Bergstrom, and J. S. Simons, A specific brain structural basis for individual differences in reality monitoring, The Journal of Neuroscience, Oct. 5, 2011, vol. 31, no. 40, pp. 14308 – 13.
“Chimpanzees do not have paracingulate sulci.” M. De Haan and M. H. Johnson, The Cognitive Neuroscience of Development, Psychology Press, 2003.
