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Counterpoints in Science

The Other People
First Neandertal Tells All

Jerold M. Lowenstein

In 1856 a strange skeleton was blasted out of a cave in the Neander Valley (Neandertal) near Düsseldorf, Germany. The skull was as large as that of a present-day human but very different in shape, longer from front to back, low and flattened on top, with prominent brow-ridges. The ribs and leg bones were heavier and stronger than those of a contemporary man.

Neandertal Man, as the skeleton was called, instantly became the nexus of a controversy that has continued for the last 143 years. Was this beetle-browed creature with the projecting face and receding chin the precursor to our own species, Homo sapiens, or did it represent an extinct sidebranch of humanity, Homo neanderthalensis?

That "first" Neandertal, it turned out, wasn't actually the first. Last summer I attended a conference on Neandertals in Gibraltar, which was celebrating the 150th anniversary of the 1848 discovery in Forbes' Quarry of a woman's skull now known to be a Neandertal, eight years before the Neander Valley bones came to light! Unfortunately, its significance was not appreciated at the time. Otherwise, we might be arguing today about Homo gibralterensis.

Darwin's great idea, published in 1859, that species arise from earlier species, change with time, and eventually go extinct, provided a framework for understanding the Neandertals. Paleontologist Thomas Henry Huxley, Darwin's friend and supporter, considered them an extinct human species. But towering over scientific thought in mid-nineteenth-century Germany was Rudolf Virchow, the father of modern pathology who became a lifelong opponent of Darwinian evolution. He belonged to the vast majority who believed that species had been created once and did not change. He diagnosed the Neandertal skeleton as that of a man suffering from rickets, a malformation of the bones due to vitamin D deficiency. Some other German scientists speculated that the deceased was a congenital idiot or a Cossack fleeing from Napoleon's army, who had crawled into the cave and died.

In later years, numerous additional Neandertals were discovered in Belgium, Croatia, and France, but Virchow stuck by his rickety guns. The concept that Neandertals were merely a pathological version of modern humanity has never completely faded away. Last December, The New York Times reported on a new theory by geographer Jerome E. Dobson, that the Neandertals were cretins suffering from iodine deficiency. According to Dobson, they didn't actually go extinct 30,000 years ago, they just changed their diet to more iodine-rich food-et voila! Their bones took on a "normal" shape, like ours.

In the past few years, there have been four major new books on Neandertals-or Neanderthals, the older spelling. The distinguished authors of these four tomes agree that the Neandertals were fascinating people who inhabited Europe and the Near East from about 300,000 to 30,000 years ago, when they went extinct. The Neandertals were muscular, heavily built, with short legs and arms, and cold-adapted like Eskimos. They lived in caves, used fire, made stone tools, and buried their dead. They apparently took care of their own, because a number of the skeletons show healed fractures or severe arthritis, conditions which would have been quickly fatal in a non-supportive environment.

Authors of these books and innumerable articles don't agree on the Neandertals' relationship to us. From the same bones and stones, many eminent experts draw opposite conclusions. Some are convinced the Neandertals were our direct ancestors. Others think they were an evolutionary dead end who left no descendants. A third, in-between position is that there was partial interbreeding between modern humans and Neandertals, so that there are still some Neandertal genes floating around in present human populations. One prominent paleontologist who supports this position claims that he sees a Neandertal when he looks in the mirror each morning!

Several hundred sites have been excavated where Neandertals lived, all over Europe and the Near East, from Spain to Israel and Iraq to Uzbekistan. Several hundred partial skeletons and thousands of stone tools have been recovered. Certainly there should be enough evidence by now to decide these questions, if they could be decided on the basis of physical anatomy and archeology.

Neandertal anatomy is distinct from our own in ways that cannot be explained merely by deficiency diseases. Aside from the skull, Neandertals differ in the shape of the jaw and pelvis. X-ray CT scanning has revealed that their inner ear bones are unique. It is significant that these identifying features are present in infant skeletons as well as adults. Deficiencies of vitamin D or iodine would be more manifest in mature adult bones than in incompletely formed infant bone.

Computer reconstruction has been applied to a Neandertal child's skull from Devil's Tower in Gibraltar. Missing pieces of this partial skull were filled in by creating mirror images of the pieces available. The computer program was able to determine brain size and show that skull thickness was greater and tooth development earlier than that of a modern child of the same age.

Israel provides some of the most enigmatic pieces of the jigsaw puzzle of modern and Neandertal relationships. Near Haifa and the Sea of Galilee, Neandertal and modern skeletons have been found in caves located close together. In the past, it was difficult to date cave materials, and it was generally assumed that the Neandertals had evolved into moderns over a long period of time.

Thermoluminescence and electron spin resonance tell a different story. These relatively new dating techniques measure the cumulative effects of radioactivity on teeth and stones. Modern-looking bones in the caves of Qafzeh and Skhul are dated at about 90,000 years old, while Neandertals from the nearby caves of Kebara and Amud are only 60,000 years old.

These dates imply that the moderns got into Israel first, and the Neandertals arrived later. They apparently lived side by side for many thousands of years, using the same types of stone tools, before the Neandertals disappeared.

This scenario agrees very well with mitochondrial DNA evidence that our species, Homo sapiens, originated in Africa about 150,000 years ago and that some groups left Africa about 100,000 years ago and began to populate the other continents. Israel is on the direct route out of Africa, and the 90,000-year-old skeletons found there are the oldest members of our species located outside of Africa.

In Europe, the kind of tools associated with Neandertals are distinctive from the tools made and used by the moderns. The Neandertals' tool kit, called Mousterian after the French cave site where they were first discovered, consisted mostly of discoid stones with their edges sharpened by flaking off small pieces, and pointed stones sharpened on the edges. The moderns' kit, called Aurignacian, is characterized by long retouched blades, short, steep-sided scrapers, and more refined tools made of bone and antler (see page 22).

If only we had Neandertal mitochondrial DNA to compare with that of living human populations, we might be able to resolve these long-simmering disputes about our relationship to them. As readers of my columns are aware, I have been doing research on fossil molecules for the past two decades, hoping to clarify these kinds of problems. Using the technique of radioimmunoassay, I have detected serum albumin in a Neandertal bone from Shanidar, Iraq. This albumin is not distinguishably different from that of living humans. Human albumin, however, is only one percent different from that of chimpanzees, too slow a "molecular clock" to reveal our genealogical relationship to the Neandertals.

A new chapter in "biomolecular paleontology" began in 1987, when Allan Wilson and his collaborators at Berkeley were able to extract mitochondrial DNA from fossils a few hundred to a few thousand years old. Mitochondrial DNA is a "fast clock" that mutates at about ten times the rate of nuclear genes such as the albumin gene. Why mitochondrial DNA changes so rapidly is not known; one hypothesis is that its repair enzymes are not as efficient as those of nuclear DNA, so that more "typos" get through without being corrected. Whatever the reason, mitochondrial DNA's rapid evolution provided the Wilson group with a stopwatch to determine the date of origin of Homo sapiens.

Two years ago a team led by Svante Pääbo, a former Allan Wilson student now at the University of Munich, succeeded in getting mitochondrial DNA from a small piece of an arm bone of the First Neandertal, the original specimen that exploded out of Feldhofer Cave in 1856. It was only fitting that the skeleton that raised so many questions should finally provide some of the answers.

The Munich molecular sleuths used the most modern techniques, the polymerase chain reaction (PCR) and bacterial cloning, to amplify DNA fragments so that these copies could then be analyzed and sequenced. They were able to reconstruct a 378-base-pair sequence, and match it with the corresponding sequence from living people. They made comparisons with almost a thousand individuals from around the world. They particularly wanted to see if Neandertal DNA shows any resemblance to that of Europeans. If so, this would support the Neandertals-as-ancestors theory. Neandertals have been found in Africa or East Asia.

To fend off potential criticism that their results might be incorrect or biased, the Munich group provided some Neandertal bone to Mark Stoneking, another former Wilson student, at Pennsylvania State University, where he and his team made an independent analysis.

Results from the two laboratories were in complete accord. The 378-base-pair Neandertal sequence differed on average from modern human DNA in 27 places. The modern human sequences differed from each other in only eight places. Moreover, the Neandertal DNA was no more similar to that of Europeans than it was to any other geographical group.

These results support only one of the three theories about Neandertals. They indicate that Neandertals were a completely separate species from Homo sapiens, four times as different from us genetically as Africans, Asians, Europeans, and Australian aborigines are from each other. The Neandertal DNA indicates that the two species, Homo neanderthalensis and Homo sapiens, had a common ancestor in Africa about 600,000 years ago. There is no DNA evidence of any interbreeding between the two species. Therefore, when the Neandertals went extinct about 30,000 years ago, their genes went extinct, too.

The few paleontologists who belong to a hard core of "multiregionalists" continue to derive their genetics from their interpretations of fossil bones and teeth. At the Gibraltar conference last August, however, attended by paleontologists and archaeologists from all over the world, not one speaker contested the DNA findings. It is important, of course, to confirm these results with other Neandertal specimens, and numerous others have been tested, but so far none have yielded any decipherable DNA. It would be a remarkable coincidence if the first Neandertal should have the last word about his own evolutionary status.

Though we know now that Neandertals were not merely a distorted image of ourselves, they were our closest relatives. Their brains were as large as ours, or a little larger, but their tools were less sophisticated and they apparently never produced the kind of cave art that burst out among Homo sapiens about 40,000 years ago in Africa, Asia, and Europe.

Unfortunately, CT scanning and mitochondrial DNA can't tell us what the Neandertals were thinking, or what ultimately gave us the evolutionary edge over them. Had they mastered language? (There's a theory that they had the wrong kind of larynx.) Did they make and wear clothes? (Their tool kits are devoid of the bone needles so abundant in the moderns' tool kit.) Did they make a last stand against their slender dome-headed competitors, or did they just fade away?

It is not likely that we'll answer any of these questions very soon. But we do now have a measure of the degree of our kinship with those stolid cousins who once flourished in the glacial climes of Eurasia and who (as endless novels and movies have imagined) were driven into extinction by our ancestors a couple of thousand generations ago.

Jerold M. Lowenstein is professor of medicine at the University of California in San Francisco and chairman of the Department of Nuclear Medicine at California Pacific Medical Center in San Francisco.

Summer 1999

Vol. 52:3