The evolution of Homo sapiens took place over many millions of years and, while some parts of it are better known than others, our knowledge of it has advanced to the point where it is possible to point to significant milestones and associate approximate dates with them. This discussion and the hypotheses I am going to advance take place in the context of this evolution. In the interest of conducting this discussion in the full context of reality, I will briefly summarize some relevant evolutionary milestones, give approximate dates for them and then treat that context as implicit for the remainder of this paper.
The first animals with mammal-like characteristics originated at about the same time as the reptiles, however the reptiles came to dominate the ecological scene of the Mesozoic Era from around 245 million years ago (hereafter MYA) up until around 65 MYA. This time has also been called the "Age of Reptiles" although it could plausibly have been called the "Age of Birds" because it now seems that the most famous faunal forms of that era (i.e. the dinosaurs) were more closely related to birds. By the middle of this era, around 170 MYA, animals with distinctively mammalian characteristics had evolved. However, it was not until the end of the Cretaceous Period, around 65 MYA, that mammals displaced the dinosaurs from their place of ecological prominence. Before that, whatever advantages mammals had over the dinosaurs were marginal as the two varieties shared a stable coexistence for more than 100 million years.
By the middle of the Miocene Epoch, around 17 MYA, the first apes had evolved in Africa. One of these, Proconsul 1 , is thought to be the antecedent of several present-day apes and is potentially a human ancestor. The nearest living relative of man is the chimpanzee or bonobo, and we share a common ancestor somewhere between 5 2 and 8 3 MYA. The genetic difference between chimpanzees and humans is less than 2% 4 , indeed we even share the same ABO blood types. Further, the development of a human child and a chimpanzee child are remarkably similar up until around two years of age. A few decades ago an experiment was performed in Italy 5 in which a chimpanzee egg cell was exposed to human sperm with the result that the egg was fertilized. This cell proceeded to divide in what appeared to be the beginning of a routine developmental process that could potentially have resulted in a human-chimpanzee hybrid. The experiment was terminated at that point. The evidence is very good that the human and chimpanzee genetic heritages are very similar and largely identical.
When Charles Darwin still lived the relationship between men and apes was stated as "We have a common ancestor." By the early 1970s, when I was taking physical anthropology in college, the relationship was stated as "We are cousins." In the early 1990s in a lecture he gave at Rice University, Richard Leakey bluntly stated "We are African apes." Jared Diamond took matters one step further when he penned his book The Rise and Fall of the Third Chimpanzee (i.e. man).
Frankly, I can find no objective grounds on which to dispute the identity of human beings as African apes. If you take away the genetic code that endows human beings with intelligence and upright posture, what you are left with is an animal very much like a chimpanzee. The various species that were involved in the evolution of man over the last 5 to 8 million years may be extinct in the sense that today no living purebred examples exist, but the genetic code of those species is almost completely intact. It is inside us, and it is continuing to function exactly as it has been functioning for the last 5 to 8 million years. To be sure, we are African apes with very high IQs, but for all practical purposes within each of us is a living simian. Any analysis of human behavior (including psychology, history and political science) that does not take this into account is done outside the full context of reality. Conceptually:
Around the beginning of the Pliocene Epoch, around 5 MYA, a new species called Ardipithecus ramidus 19 evolved in Africa. This species was followed by a whole series of Australopithecine species from which ancestral human stock ultimately derived. Exactly where the branch took place is contested, but by around 4.2 MYA a species called Australopithecus anamensis 20 was walking upright. It seems likely that by that point in time human ancestors were walking upright also. By around 3.0 MYA a species called Australopithecus africanus 21 , although generally not considered ancestral to man 22 , was making crude stone tools. This last statement has been the subject of dispute in anthropological circles, but the latest evidence is that Australopithecus africanus was indeed a tool maker. It seems plausible that the ancestors of man could have been making crude stone tools around this point in time.
The first generally conceded human ancestor is named Homo habilis, and that species existed between 2.4 and 1.5 MYA 23 . Homo habilis made stone tools and is thought to have had language. 24 So far as is known, Homo habilis never ventured outside Africa.
The Homo habilis lineage led to Homo erectus and that species existed between 1.8 25 MYA and 400,000 years ago (hereafter KYA). One recent hypothesis holds that Homo erectus may have survived up until as recently as 30 KYA. Homo erectus knew the use of fire. Whether Homo erectus evolved in Africa or evolved as part of a distributed Afro-Asian event is currently being disputed. What is not disputed is that Homo erectus was the first hominid to live outside Africa.
The fossil record between the last known Homo erectus fossils and the Neanderthals is poorly populated. Some anthropologists hold that another species called Homo heidelbergensis 26 belongs in this gap. Others argue that Homo heidelbergensis is really Homo erectus, and still others argue that Homo heidelbergensis is an obsolete anthropological reference. I am sticking with the term simply to have a convenient reference point for further exposition. What we know for certain is that both the Neanderthals and Homo sapiens evolved from a continuing hominid lineage.
About 600 KYA the ancestors of the Neanderthals appeared. The Neanderthals lived between 200 KYA 27 and 30 KYA. Whether they should be counted as a variety of Homo sapiens has been disputed, but most anthropologists presently refer to them as Homo neanderthalensis. 28 Most recently genetic analysis has shown that their genetic heritage is significantly different from the human. This analysis places the split from the Homo heidelbergensis lineage at around 600 KYA while our own break with that lineage dates to around 250 KYA. While the resemblances between the Neanderthals and ourselves is remarkable, there were some noteworthy differences. Our ancestors had greater creative abilities than the Neanderthals as evidenced by a much more rapid progress in developing stone tools and from the much greater artistic heritage they left behind. Neanderthals may have had music, but they left nothing in the way of sculpture or cave painting. Their vocal apparatus was well enough developed to allow speech, although the areas of the brain that support speech in Homo sapiens were less developed in the Neanderthals. It now seems highly likely that Homo sapiens and Homo neanderthalensis never interbred and that Homo sapiens had marginal competitive advantages that caused a slow decline in Neanderthal populations over a period of about 20,000 years that ended in their extinction some 30 KYA. This does not mean that we are not carrying Neanderthal genetic material; quite the contrary. Somewhere in the past Homo sapiens and Homo neanderthalensis had to have had a common ancestor and hence must necessarily have a great deal of genetic material in common.
The earliest forms of archaic Homo sapiens date to around 200 KYA, and by 100 KYA fully modern humans existed in Africa. Although our ancestors made more rapid progress in developing stone tools etc. than the Neanderthals, their rate of technological progress was still incredibly slow by today's standards. Around 10 KYA our rate of technical progress began to accelerate, and then, during the Renaissance, it accelerated still more. Today, more than half of all the scientists that have ever existed in the history of the human race are alive and on the job.
I have been given to understand that Ayn Rand was uncomfortable with the idea that humans had evolved from apes. She need not have been. I hope to demonstrate that there is an objective basis for the notion that many of the human short-comings that Ayn Rand denounced are direct products of a simian heritage that has not been even marginally understood, much less consistently managed in a constructive manner.
|
1 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 207 return |
|
2 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 295 return |
|
3 |
Donald Johanson and Blake Edgar, From Lucy to Language (New York; Simon Schuster Editions, 1996) p. 111 return |
|
4 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 310 return |
|
5 |
There are actually two references for this information: (1) Information obtained from a news broadcast on a radio station (probably WCOL) in Columbus, Ohio in the late 1960's or early 1970's. It was probably a wire story from a European wire service. (2) May 14, 1987 issue of the Houston Chronicle, Page 14, Section 1, in a story headlined "New breed of half-ape 'slave' thought possible." The story was a reprint of a story by one Uli Schmetzer of the Chicago Tribune. Brunetto Chiarelli, dean of anthropology at Florence University said that he had knowledge of a secret experiment in which a chimpanzee egg was exposed to human sperm with the result that an apparently viable embryo was created. The experiment was interrupted at the embryo stage because of ethical considerations. "Scientific information is numerous but reserved. Maybe at the end of the year we will have an idea of what has been achieved," Chiarelli said. return |
|
19 |
Donald Johanson and Blake Edgar, From Lucy to Language (New York; Simon Schuster Editions, 1996) p. 38 return |
|
20 |
Jim Foley, The Talk Origins Archive http://www.talkorigins.org return |
|
21 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 236 return |
|
22 |
Donald Johanson and Blake Edgar, From Lucy to Language (New York; Simon Schuster Editions, 1996) p. 38 return |
|
23 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 242 return |
|
24 |
Goran Burenhult The First Humans American Museum of Natural History (U.S.; HarperSanFrancisco, 1993) p. 46 return |
|
25 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 243 return |
|
26 |
Goran Burenhult The First Humans American Museum of Natural History (U.S.; HarperSanFrancisco, 1993) p. 49 return |
|
27 |
Goran Burenhult The First Humans American Museum of Natural History (U.S.; HarperSanFrancisco, 1993) p. 66 return |
|
28 |
Steve Jones, Robert Martin, David Pilbeam, The Cambridge Encyclopedia of Human Evolution. (U.K.; Cambridge University Press, 1992) p. 247 return |