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

Time to jettison the "common ancestry" theory?

A. anamensis skull

Archaic humans show a range of physical features that are found in modern humans. Those features include high broad foreheads, low receding foreheads, low cheek bones, high cheek bones, protruding chin, cranial size generally proportional to body size, dentition within the range of primitive and modern humans, and hands and feet like modern humans.

That assessment of the data is leading paleoanthropologists to rethink the prevailing evolutionary theory, according to this recent statement made by Hester Hanegraef.

"Discoveries all over the world in the last decade have led to a complete rethinking of our evolutionary past. It shows that new fossils do not always support existing hypotheses, and that we must be prepared to change our views and formulate new theories based on the evidence at hand."

Note the protruding jaw of this eighth century BC blacksmith.

The 1500 bones and bone fragments recovered by the Rising Star Expedition belonged to at least 15 individuals. The adults were about 5 feet tall. Parts of the skeletons resemble modern human anatomy while other skeletal remains resemble the australopiths, like Lucy. In other words, this burial pit contained the remains of people who ranged in appearance about as much as modern humans.The bones/bodies were ritually deposited over “some period of time.”

This 250,000 year hand of Homo naledi is virtually identical to that of modern humans.

This find is being presented as a "new branch" of homo, called Homo naledi. H. naledi is viewed as slightly more human than the A. australopithecine and slightly less human than modern humans.

Jeffrey Schwartz thinks that the H. naledi remains represent two or more different species. He makes his case in Newsweek: “Why the Homo Naledi Discovery May Not Be Quite What it Seems”. 

On the other hand, John Hawks states that "The variation within the collection is not high, it is extraordinarily low." Hawks reports: "Homo naledi has a mosaic of features that include some that compare most closely to more primitive australopiths, and others that compare more closely to Homo. How do we know that this is one species rather than a jumble of species mixed together? Simple: every feature that is repeated in the sample is nearly identical in all individuals that preserve it."

Similar speculation arises around A. anamensis. This find has been in the news this week. A. anamensis lived approximately between 4.2 and 3.8 million years ago. Nearly one hundred fossil specimens are known from Kenya and Ethiopia, representing over 20 individuals.

The shape of the end of this lower leg bone, or tibia, indicates that A. anamensis walked upright. Most features align with those identified with A afarensis. The teeth in this jawbone are large relative to the body size of A. anamensis. The back teeth are also large relative to the front teeth. Both primitive traits are characteristic of all Australopithecus.

Hester Hanegraef notes that A. anamensis and A. afarensis overlap for at least 100,000 years, "making it impossible for A. afarensis to have evolved gradually from one single ancestral group. In fact, it is becoming increasingly obvious that most species on our evolutionary lineage likely evolved by branching off from existing groups." (Read more here.)

The question remains: Do these early Homo fossils represent stages or branches of evolutionary development from a common ancestor, or do they represent archaic humans with the same range of physical diversity as modern humans?

Related reading: Spinners of Evolutionary Fictions; Genesis Has No Evolutionary Framework