Homo sapiens—The First Humans

Homo sapiens—The First Humans

Lecture 21

Recent analyses of DNA extracted from Neanderthal skeletons suggest something very, very clear indeed. It suggests that Neanderthal and human lines split more than 500,000 years ago—maybe 600,000 or 700,000 years ago. And what that suggests is that we really are talking about different species. We’re not talking about minor variations on the same species. And that evidence also seems to rule out any possibility that humans and Neanderthals interbred.

So, here we are. Though tantalizingly close to us, neither ergaster nor Neanderthals display quite the technological creativity that is the birthmark of our species, nor apparently the ability to communicate with the uency, precision, and speed of modern humans. Both species disappeared about 20,000 to 30,000 years ago, probably under pressure from our species.

The last lecture suggested that our astonishing ecological creativity arises from our capacity for “symbolic” language, which allows us to learn collectively. If this argument is correct, how can we tell when the rst real humans appeared? What evidence could show the presence of symbolic language and a new level of ecological and technological creativity?

Unfortunately, the evidence is so sparse and hard to interpret that we have few unambiguous answers. This makes it important to be clear about the sort of evidence we are looking for. In principle, we can imagine two main types of archaeological evidence that might show that the threshold to collective learning has been crossed. The rst is evidence for symbolic language. Of course, language leaves no direct archaeological traces. But it may leave indirect traces. Studies of the base of the skull show how the larynx was placed, which can suggest how well a species could manipulate sounds. Sculpture or cave (or body) painting may indicate that a species was capable of symbolic thought and language.

The second type of evidence is anything that might show an acceleration in innovation or adaptation, or increasing variety in the technologies used by different human communities. Unfortunately, early evidence of accelerating technological change is scarce and ambiguous, particularly from Africa, where our species probably evolved.

Fossil evidence for most of the last million years is dominated by two other hominine species, Homo ergaster and Homo neanderthalis. Could they speak? And could they adapt with the virtuosity of modern humans? We saw in Lecture Eighteen that ergaster evolved almost 2 million years ago. Some migrated to Indonesia and China. They probably used re, and certainly used “Acheulian” stone tools, which were better made than the “Oldowan” tools of Homo habilis. This is evidence of technological creativity but not of exceptional creativity. Other species (including apes such as orangutans) had migrated from Africa to Asia; evidence on ergaster control of re remains limited, and their stone tools barely changed over 1 million years.

Homo neanderthalis seem even closer to us. Neanderthals lived in ice age Europe and Russia. They were as tall as us and had brains as large as ours (perhaps even larger). They also manufactured more delicate and precisely made stone tools described by paleontologists as “Mousterian.” They probably used re and hunted large ice age mammals such as mammoth and woolly bison, which was no small feat!

Yet their technologies show limited variation over 200,000 to 300,000 years, and there is no proof that they had symbolic language. Indeed, studies of Neanderthal skulls suggest that their larynx would not have allowed them to speak like we do. (However, there is somewhat controversial evidence that Neanderthals buried their dead, which might imply a capacity for symbolic thought.) Recent analyses of DNA extracted from Neanderthal skeletons suggest that Neanderthal and human lines split more than 500,000 years ago.

Though tantalizingly close to us, neither ergaster nor Neanderthals display the technological creativity that is the birthmark of our species. Both species disappeared about 20,000 to 30,000 years ago, probably under pressure from Homo sapiens.

Currently, there are two competing explanations for the origins of Homo sapiens. The “multi-regional hypothesis,” defended by Milford Wolpoff and Alan Thorne, argues that our species evolved gradually throughout Africa and Eurasia from Homo ergaster. It implies that most hominines in this era belonged to a single, evolving species, with regional variants that show up today in racial differences. However, most anthropologists are skeptical that individuals could remain suf ciently interconnected over such large distances to remain a single species.

At present, most paleontologists prefer the “Out of Africa” hypothesis, according to which our species evolved quite rapidly in Africa within the last 250,000 years. This theory builds on recent developments in evolutionary thought and dating techniques. In their theory of “punctuated equilibrium,” Stephen Jay Gould and Niles Eldredge showed that the pace of evolution can vary signi cantly, so that sometimes new species can evolve within thousands rather than millions of years.

One mechanism for rapid evolutionary change is “allopatric speciation.” If individuals at the edge of a species’ range get cut off for many generations, they may diverge rapidly from a parent population because variations can spread rapidly in small populations. Besides, such groups may already be statistically atypical. Allopatric speciation may explain the rapid species formation Darwin observed on the Galapagos Islands and the sudden appearance of modern humans.

Modern genetic dating techniques show that modern humans are closely related and probably evolved within the last 250,000 years. The fact that the greatest variation appears within Africa suggests that that is where humans have lived longest. Finally, the earliest fossil evidence of anatomically modern humans comes from Africa, and the oldest remains of modern humans are about 160,000 years old.

I will argue in the rest of this course that human history really begins between 200,000 and 300,000 years ago, somewhere in Africa.

Perhaps we appeared even more recently? Archaeological evidence seems to show an acceleration in technological change in Europe and Russia about 50,000 years ago. Improved stone tools appeared, as did new materials including bone and skins. Cave paintings and carved objects provide evidence of symbolic thought. Some specialists argue that this “Revolution of the Upper Paleolithic” proves that even if Homo sapiens evolved earlier, modern human behaviors appeared only 50,000 years ago, perhaps as a result of tiny changes in the wiring of the brain. If this is correct, then the critical threshold may have been crossed—and human history would have begun—just 50,000 years ago.

I am not a paleontologist, but recent work by two paleontologists, Sally McBrearty and Alison Brooks, has convinced me that the good money is on the “Out of Africa” hypothesis. So, with a warning that opinion could change if new evidence appears, I will argue in the rest of this course that human history really begins between 200,000 and 300,000 years ago, somewhere in Africa. What’s the evidence for this conclusion?

McBrearty and Brooks argue that the “Revolution of the Upper Paleolithic” is an illusion, created simply because much more archaeology has been done in Europe than in Africa. Their detailed survey of the scanty archaeological evidence from Africa suggests that the technologies that appear in the Upper Paleolithic had already evolved in Africa. From almost 300,000 years ago, new technologies, and even hints of symbolic activity (such as the use of ocher), appear in association with a new hominine species, Homo helmei, which they regard as an early version of Homo sapiens. Blombos cave in South Africa offers a good illustration. It was occupied from 70,000 years ago. Its inhabitants used ocher (presumably to paint their bodies) and made ne stone tools. They used shell sh and may have shed.

The details of how our species evolved remain unclear, but currently the bet is on a rapid appearance of modern humans about 200,000 to 300,000 years ago, somewhere in eastern or southern Africa. The next lecture asks: How did the rst humans live during the earliest phase of human history—the Paleolithic era?

Essential Reading

Supplementary Reading

Questions to Consider

Christian, Maps of Time, chap. 7. ———, This Fleeting World, chap. 1. Fagan, People of the Earth, chap. 3.

Lewin, Human Evolution. McBrearty and Brooks, “The Revolution That Wasn’t.” Ristvet, In the Beginning, chap. 1.

1. What are the most powerful reasons for thinking that our species appeared between 200,000 and 300,000 years ago in Africa?

2. What reasons are there for arguing that Neanderthals were not fully human?