by Paul Garner
The second programme in the series, ‘Blood Brothers’, took us to what it described as “a crossroads in our evolution”. According to the evolutionary framework, there were several species of “ape-men” living on the East African savannah two million years ago. But what do we really know about these creatures? Were they really transitional between apes like ‘Lucy’ and ourselves? Do they really deserve the epithet “ape-men”? Let us dig a little deeper and find out.
Paranthropus boisei – a specialized ape
The original specimen of this species – what scientists refer to as the ‘type specimen’ – is a skull (OH 5) found in 1959 by Mary Leakey at Olduvai Gorge in Tanzania.1 Other important boisei fossils are skulls KNM ER 406 and KNM ER 732, thought to be a male and female respectively.2
This creature was, in truth, nothing more than a robust type of australopithecine (the group of apes to which Lucy belonged). The robust variety is distinguished from other australopithecines by its greater size and the massive jaws and teeth. The skull bore a bony crest to which powerful muscles for chewing were attached. Despite boisei’s great bulk, its brain was actually not much larger than in other australopithecines – about the same as the modern gorilla. In fact, boisei appears to have been a rather gorilla-like animal. Although Walking With Cavemen showed boisei eating tough roots, a study of the teeth by Harvard scientist Alan Walker seems to contradict this:
“Walker’s study of the enamel thickness and surface microwear show no scratches that could be associated with a diet containing soil particles or bone. This seems to rule out meat, root and even herb-leaf eating. The thick enamel would have protected the tooth from cracking if very small hard seeds were present. Walker therefore sees the robusts as predominantly eaters of fruit, both soft- and hard-cased, possibly in less open but more wooded environments.”3
As the programme conceded, Paranthropus boisei was not our ancestor. In the words of Tomkins:
“The robust australopithecines, represented first by the Paranthropus specimens of Broom from South Africa, have long been problematic but now clearly appear to be a side issue so far as human evolution is concerned.”4
Homo habilis and Homo rudolfensis – a story of confusion
According to Walking With Cavemen, the ancestry of modern humans must be sought in one of the other “ape-man” species inhabiting the savannah: Homo habilis. Some experts regard certain forms within the Homo habilis group as distinctively different and, for some years, they have been given a separate name (Homo rudolfensis). Although it was not obvious from the television programme, there is a great deal of controversy about these creatures. The confusion arises partly because the fossil remains are so fragmentary:
“The fossil evidence of early members of the genus Homo is scanty and not as well defined as would be desirable.”5
It has recently been pointed out, for instance, that no postcranial fossils (i.e. anything from the neck down) can be reliably attributed to Homo rudolfensis.6
Some experts think that both habilis and rudolfensis are actually types of australopithecine.7Certainly in overall size and body proportions, locomotion, jaws and teeth, dental development, and brain size, most of the fossils attributed to these creatures are similar to those of the living great apes and unlike those of modern humans.8 A possible exception to this is skull KNM ER 1470. This specimen has an estimated brain size that approaches that of modern man (750-800 cc). There is also evidence from inside the skull of a Broca’s area, the part of the brain that controls speech. Based on the available material, this skull may have belonged to a true human.
Walking With Cavemen portrayed Homo habilis as an opportunistic scavenger and suggested that it was being a “jack of all trades” that gave habilis the advantage over boisei. However, the evidence that early humans passed through a scavenging phase is equivocal.9 The stone tools that are associated with the habilines are surprisingly sophisticated but the available evidence does not allow us to deduce who made them. The fact that habilis remains are found associated with stone tools does not necessarily mean that habilis made them.
The second Walking With Cavemen programme introduced us to three of the so-called “ape-man” species living in East Africa in the past. The first of these, Paranthropus boisei, was a gorilla-like animal unrelated to modern humans. The other two types were classified as ‘early Homo’ but it is increasingly clear that this category is a rag-bag assortment of fossils, most of which closely resemble australopithecine apes. As a transitional stage in human evolution it is unconvincing. The imaginative reconstructions in Walking With Cavemen obscure the fact that there remains a large gap between ape-like creatures and true humans in the fossil record and that convincing intermediates are missing.