In yesterday’s first post in this occasional series, I mentioned the geological dating of the site of Olduvai Gorge in northern Tanzania—one of the most significant events in the history of discoveries in the human fossil record, and one which helps to illuminate the nature of creationist opposition to evolution more generally.
On today’s date, September 26, in 1931, Louis S. B. Leakey (1903–1972) first visited Olduvai Gorge, a site which is now world-famous as the source of important fossils and stone tools from an early, although we now know far from the earliest, stage of human evolution. In 1931, however, Olduvai was essentially unknown, and almost no human fossils had been found anywhere in Africa. Fossil mammals had been collected at Olduvai by German scientists before World War I, when the then-Tanganyika was a German colony. From the extinct species it was deduced that the geological deposits were from the Pleistocene, but no one knew their age in absolute years. The Germans had also collected a very modern-looking human skeleton that, if actually of early or middle Pleistocene age, would have been a very ancient Homo sapiens specimen, perhaps the oldest known. (This skeleton was later determined to be an intrusive burial of a relatively recent human into much older geological layers, and so irrelevant to human evolution.)
No scientists had visited the site since the end of World War I and the political transfer of Tanganyika from German to British control. Almost immediately upon arrival at Olduvai, Louis Leakey began to collect Paleolithic stone tools from the same Pleistocene layers that contained various extinct mammals. The Germans had not recognized the relatively crude tools, but Leakey was a trained archaeologist. Thus began decades of intermittent research in the Olduvai region by Louis, joined later by his second wife Mary, their sons, and many other colleagues. He had some of the oldest known human artifacts, early Pleistocene stone tools, and he was persistent in searching for remains of the toolmakers themselves.
It wasn’t until 1959 that Mary Leakey found Olduvai’s first really substantial hominid specimen, the well-known “Zinj” skull. Soon thereafter the first few remains that would eventually be named Homo habilis were also recovered. All these were found relatively low in the geological sequence, among the oldest layers, but still no one knew exactly how old they were. At the time the general view among geologists was that the Pleistocene period, recognized around the world, might be as much as a million years old, and that the entire archeological and paleontological record of human evolution was limited to the Pleistocene and thus less than a million years in length.
Enter our second character for today, Garniss H. Curtis (1919–2012). Curtis spent most of his career as a professor of geology at the University of California, Berkeley. In the 1950s he was one of the key developers of the potassium–argon method of dating materials, especially volcanic rocks, based on the radioactive decay of potassium into argon. Other decay methods, such as one using uranium and lead, had already provided a general framework for the age of the earth in the 1930s, but were difficult or impossible to use with relatively young rocks like those of Pleistocene age. After World War II, various labs around the world explored new techniques suitable for dating younger rocks (assuming one considers one to two million years to be “young”), and Curtis was a leader in this trend.
Luckily, the rock layers at Olduvai contained the products of eruptions from a nearby volcano that were suitable for potassium–argon dating. In a series of publications in the early 1960s, Curtis and colleagues showed that the lower levels at Olduvai, including the earliest artifacts and hominid fossils, were not a million years old, but approximately 1.75 million years. The time frame of human evolution was nearly doubled at a stroke.
And how is all this related to creationism? Right around the same time that Olduvai Gorge and the scientific record of human evolution were being successfully dated by Curtis and others, the young-earth creationist movement in America was rapidly being promoted through the establishment of the Institute for Creation Research and the activities of other fundamentalist ministries. Today the majority of anti-evolutionists in America are young-earthers who not only reject the concept of human evolution but who also, although they will not admit it, implicitly reject essentially all of science.
Because their interpretation of the Bible leads them to the conclusion that life, the earth, and the universe as a whole cannot be more than about 10,000 years old, young-earthers are forced to deny that radioactive or other scientific techniques which demonstrate a universal time frame in the billions of years are correct. And to do this they must deny that physicists, chemists, and geologists, as well as biologists and anthropologists, are correct about much of anything, because the concepts and principles which underlie radiometric dating techniques are the same ones basic to all of science. Young-earth creationists have a bedrock conclusion, the young earth, and any data, evidence, or interpretation that contradicts it is ignored, denied, or waved away. Science is ready to change its conclusions when necessary; creationism is ready only to remain unchanged.
On this coming Sunday, September 29, there will be a memorial celebration of the life of Garniss H. Curtis at the Faculty Club on the University of California, Berkeley, campus. (Full disclosure: I knew Garniss after his retirement from Berkeley, when for a few years we were both on the staff of the Institute of Human Origins. He was an interesting guy.)