What Paleoanthropologists Want to Discover

 

This image depicts the "linear evolution theory" and is called the "March of Progress" image. However, the evidence of many groups of archaic humans living at the same time requires a new hypothesis. The linear evolution theory was dismissed 50 years ago. If similar images appear in science texts, it reveals how most textbooks are 40-50 years behind the front edge of the sciences.

Dr. Alice C. Linsley

Paleoanthropologists recognize that there were many groups of archaic humans. Among them were the Neanderthals and the Denisovans. A recent genome study revealed that the Denisovans "diverged from Neanderthals 400,000 years ago and that at least two distinct Denisovan populations mixed with ancestors of present-day Asians."

There are limited physical remains of Denisovans. These include a finger bone, three teeth, and a skull fragment from the Denisova Cave; and a jawbone and the Xiahe mandible from Baishiya Karst Cave at the northeastern Tibetan Plateau.

In a November 8, 2024 interview, Dr. L. Ongaro said, “It’s a common misconception that humans evolved suddenly and neatly from one common ancestor, but the more we learn the more we realize interbreeding with different hominins occurred and helped to shape the people we are today."

Richard Leakey long ago abandoned the linear evolution misconception, saying:

Current findings on human evolution have brought us to the position where much of what we believed to have theoretically happened proves to be incorrect. Much that is in the textbooks, much that is still being taught in universities about human evolution is no longer true, but it continues to be taught because the implications of recent discoveries are insufficiently understood.

It was principally Weidenreich, Le Gros Clark, and a few of the people of that generation, just previous to mine, who put forward and strongly defended the idea that man had gone through a very simple series of stages of evolution: the pongid stage, an Australopithecine stage, a Pithecanthropus stage, and then man as we know him today. Theoretically, this had always seemed highly unlikely to some of us, since it meant that man had done something which no other mammal had done: evolved in a single straight line instead of having one main branch, with many experimental side branches which failed to make the grade. Yet the old theory persists. Linked with it is the concept, still very, very widely taught and very widely believed, that man in the relatively near past was at a pongid or ape stage of evolution. In such a very short time, three or four million years, as the books and many of my colleagues put it, we are supposed to have lost our huge canine teeth, lost our simian shelves, lost our long, brachiating arms, ceased to dwell in the trees, and many other similar but, I fear, erroneous concepts. These were theories which in the light of current facts no longer stand up."

Anthropologists such as John Hawks note that there is a wider range of anatomical features among Neanderthals than is generally recognized. Hawks also believes that there are limits to what can be determined by genetic tests of archaic fossils. He relies on morphological studies. 

The story of human origins cannot be understood from DNA alone. That can take us back only to about 500,000 years ago. What about the humans who lived before that? We have artifactual evidence of humans that date to over 500,000 years ago. Some human fossils found in Eastern Africa date to well before 500,000 years ago.

When Jeremy DeSilva, a British anthropologist, compared the ankle joint, the tibia and the talus fossils of human ancestors ("hominins") between 4.12 million to 1.53 million years old, he discovered that all of the ankle joints resembled those of modern humans rather than those of apes. Chimpanzees flex their ankles 45 degrees from normal resting position. This makes it possible for apes to climb trees with great ease. While walking, humans flex their ankles a maximum of 20 degrees. The human ankle bones are quite distinct from those of apes.

The discovery of a complete fourth metatarsal of A. afarensis at Hadar that shows the deep, flat base and tarsal facets that "imply that its midfoot had no ape-like midtarsal break. These features show that the A. afarensis foot was functionally like that of modern humans." (Carol Ward, William H. Kimbel, Donald C. Johanson, Feb. 2011) 

The Ward, Kimbel and Johanson study reveals how scientists can change their minds. Donald Johanson was the person who announced to the world that Lucy was "ape of the South" or Australopithecus. Has he since reconsidered that assessment?

Excavations at the Boker Tachtit archaeological site in the Negev Desert revealed that modern humans and Neanderthals lived together.

Today various groups of Australopithecus are recognized. Some are gracile and others are robust. There are Australopithecus afarensis (including Lucy), Australopithecus africanus, Australopithecus anamensis, Australopithecus sediba, Kenyanthropus platyops, and "robust" specimens like Paranthropus robustus and Paranthropus aethiopicus.

In 2011 researchers discovered jaw bones and teeth of four individuals in the Afar region of Ethiopia that date to between 3.3m and 3.5m years. These archaic humans were alive at the same time as other groups of early humans, suggesting that it is time to abandon the linear evolution hypothesis. Clearly, there were more archaic humans living 3 million years ago than is generally recognized. How they may be related is the great question facing paleoanthropologists.

Related reading: A look at the Neanderthal from Altamura, John Hawks; Can Molecular Models be aligned with Human Morphology?; Many Groups of Archaic Humans (video); Ancient human ancestor Lucy lived alongside at least 4 other proto-human species | Live Science; “Lucy”, superstar of evolution, at fifty; When hominins walked in each others' tracks

Was Lucy Human?

Donald Johanson and Maurice Taieb (with camera) in 1974, studying the bones of an Australopithecus afarensis specimen later named "Lucy".

Alice C. Linsley

Dr. Jeremy De Silva's research has shown that Australopithecus lacked the large grasping toe typical of tree climbers, and its spine, pelvis, knees, and ankles were made for walking on two legs and not designed for tree climbing.

A recent discovery of a complete fourth metatarsal of A. afarensis at Hadar shows the deep, flat base and tarsal facets that "imply that its midfoot had no ape-like midtarsal break. These features show that the A. afarensis foot was functionally like that of modern humans." (Carol Ward, William H. Kimbel, Donald C. Johanson, Feb. 2011) Read the report here.

Additionally, A. afarensis apparently used polished bone tools, had communal meals, and controlled fire. Some of the earliest evidence of controlled use of fire by humans was found at Swartkrans in South Africa. Other sites that indicate fire use include Chesowanja near Lake Baringo, Koobi Fora and Olorgesailie in Kenya.

A. Afarensis also had human dentition which is quite easily distinguished from that of apes. In humans, the back teeth are larger than the front teeth (not so with apes), and the canines are not pointed. Humans also lack the characteristic diastema or tooth gap found in apes.

Mary Leakey’s 1979 discoveries in Tanzania added to the evidence that humans walked the earth about over 3 million years ago. At Laetoli, about 25 miles south of Olduvai Gorge in Tanzania, Leakey discovered footprints of a man, woman and child created about 3.6 million years ago and preserved under falling ash from the nearby Sadiman volcano. The raised arch and rounded heel of the footprints showed that whoever left these footprints walked as humans today.

However, Donald C. Johanson (co-author of the Feb. 2011 report cited above) had already declared to the term Australopithecus meaning "ape of the south" or "southern ape". Mary Leakey might have objected. She later expressed her regret that “the Laetoli fellow is now doomed to be called Australopithecus afarensis.”

Johanson and Mary Leakey were scheduled to speak at a Nobel Symposium in Sweden in May 1978. The conference honored Mary Leakey, who received the Golden Linnaean Medal from the King of Sweden for her scientific investigations. Mary Leakey was embarrassed when Johanson announced the name - Australopithecus afarensis - for his Afar Triangle finds and included Mary Leakey's 4-million-year Laetoli specimen (jawbone LH4) from Tanzania as an exhibit.

Johanson, who was scheduled to speak before Mary Leakey, scooped her speech. She was upset because Johanson's designation of "ape" was at odds with what she believed to be the evidence. Johanson's label for Lucy and her community stuck though he clearly has doubts based on more recent discoveries as to the accuracy of the ape designation.

The designation of ape is contradicted by the evidence that these archaic humans had oppositional thumbs, short fingers, human dentition, walked upright, and controlled fire. Discoveries in Dikika, Ethiopia indicate that they used flints to scrap, saw, and chop. Two fossilized bones have been found that appear to be marked by stone tools. On the basis of low-power microscopic and environmental scanning electron microscope observations, these bones show unambiguous stone-tool cut marks for flesh removal and to access bone marrow.

The evidence suggests commensality: sharing a meal around a fire. That is a human practice, not one of apes.

Muscle reconstruction provides further evidence that Lucy walked as modern humans do. 

The evidence taken together indicates that Lucy and her community were human, though anatomically archaic humans. What do you think?


Related reading: Maurice Taieb, the Geologist who Discovered the Site Where Lucy was Found; Genesis and Genetics; Biblical Anthropologists Discuss Darwin; The Evolution of Darwinian Evolution; Getting the Facts About Human Origins; Is Genesis Really About Human Origins?