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11. Inheriting the Earth

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11. Inheriting the Earth 11 INHERITING THE EARTH Having established a zoological ancestry for humanity, countering the fundamental religious argument that we are unique and outside of nature, we follow the paths that humans have travelled out of Africa. Originating in Africa, humanity undertook a series of migrations, spreading through Europe and Asia, finally arriving in Australia and the Americas. At some point a suite of evolutionary changes occurred that separated one line of hominins from their close relatives, with unforeseeable consequences. Perhaps the need to accommodate to the rapid – from an evolutionary point of view – enlargement of their brains or to some other change in their environment, such as diet, our ancestors began to enter the world in an immature and defenceless condition. At another time and in another place, this could have been an evolutionary calamity, but it was accompanied by other changes to protect the newborn, including intense maternal care. A process of neoteny, not uncommon in evolution, had begun. The change proved not to be the disaster it might have been. The babies had the potential to grow large brains, unhampered by premature hardening of the brain case. Early birthing also allowed a baby’s head to fit better in the birth canal. The downside was that the hominins had to spend more time and effort in rearing their young successfully. We are now remarkable among animals for the years of work we put into our children. 163 CooperaTive evoluTioN It turned out in the end to be a great evolutionary success. The changes led eventually to all we take for granted in our human condition. Of course, one thing does not change in isolation. The need for prolonged child care created a selection pressure for greater cooperation within the family group to provide for and protect nursing mothers. And there were physical changes as well, developmental changes that once happened in utero that now happened in early childhood. These characteristics, once isolated from the environment, were exposed to it and subject to its influences. Our ancestors, it seems, were the first hominins to show this form of evolution, called neoteny. It is essentially the retention of juvenile features into adulthood. It is a phenomenon that exposes persistent embryonic features to direct natural selection. Other primate species do not experience this as intrauterine development produces newborns with more advanced muscular development. The idea thatHomo sapiens is a neotenic chimpanzee is an idea of some antiquity. In 1929, a Dutch anatomist, Lodewijk Bolk, first drew up a list of the probable neotenic characteristics that we, as adults, display: 1. A rounded, bowl-shaped cranium to house a brain that will grow to about four times its volume at birth. 2. A juvenile face that lacks the brow ridges and the heavy jaw development that is characteristic of adult apes. 3. The spinal cord enters the skull at a point vertically underneath it and does not move towards the back during development, thus making an upright stance possible. 4. Late closure of skull sutures and persistence of cartilaginous bone ends (epiphyses) into early adulthood. 5. In women, the vaginal canal does not rotate backwards, as it does in chimpanzees, but remains directed forward. 6. A big toe that remains aligned with the other toes and does not rotate sideways and become opposable, like a thumb. Compared with our simian cousins, our skeleton is under-developed at birth, with cranial sutures not yet joined, and uncalcified ends to the long bones which do not fuse together until puberty and a ‘straight’, rather than a grasping, big toe. An unfortunate legacy, a backbone better suited to walking on all fours than standing upright is still a human drawback today. 164 11. iNHeriTiNG THe earTH In women, the reproductive tract does not rotate rearwards, as in apes. Its more forward position facilitates face-to-face sexual and other communication. All this was accompanied by a period of intense social evolution that paved the way for collaborating communities. It must be said that this appealing concept is not without its critics. Shea (1989) considered the evidence, and concluded that there was a case, but it was ‘relatively weak’ (which might be interpreted as ‘quite strong’ depending on your point of view!). So now, equipped with a bipedal posture made possible by longer legs and changes to the skull, combined with a Palaeolithic tool kit that included stone points, hand-held axes and fire-hardened spears, ancient humans were ready to leave Africa. Recent fossil evidence from Morocco suggests that archaic Homo sapiens were in north Africa as much as 300,000 years ago (Hublin et al. 2017). According to Groves (pers. comm.) ‘modern’ humans appeared first in Africa and began their migrations into Europe and Asia about 80,000 years BP (before present). Evidence for this comes from ‘modern’ human fossils found in the Middle East, suggesting the trip was made from the Horn of Africa to the Arabian Peninsula by rafts or by island-hopping, or even walking, when the sea level was about 70 metres lower than it is today. This was a trip that other non-sapiens hominins had made much earlier. For example, the diminutive ‘hobbit’ had already drifted as far as Indonesia. Argue and colleagues (2017) conclude that the most likely origin for the ‘hobbit’ is from an early Homo lineage, such as Homo erectus, who wandered all over Africa, but also made it out of Africa and into Asia. Its most recent fossils in Asia are dated at 140,000 BP. The Neanderthals were in Europe and Asia 400,000 BP, and persisted until 40,000 BP, making them partly contemporaneous with modern humans. Cohabitation probably accounts for the Neanderthal genes we possess. The fact that the date for the exodus from Africa ofHomo sapiens is set around 80,000 years ago is consistent with the new estimates for human arrival in northern Australia. This is ample time for humans to have made the trip given the built-in error in the age estimates. The very recent discovery of polished stone axes dated to 65,000 BP, and other artefacts, such as the presence of red ochre for decoration and/or ritual purposes, suggests that modern humans – Aboriginals – were in Australia at least 10,000 years earlier than previously thought. 165 CooperaTive evoluTioN The first scanty suggestions of human abstract thought come from well before the last ice age. The carefully laid-out body of Mungo man in Australia, from 40,000 years ago, supports this. More recently, even clearer evidence of abstract thought is found in the cave paintings in Australia, France and Spain. The images are of animals and food sources, and other symbols of social custom. It has been suggested that these cave drawings were intended to increase the luck of the hunters, to show respect for others or to invoke help from spiritual beings. A stone figure of a plump woman, the ‘Venus of Willendorf’, carved 28,000 years ago, might have served all three purposes. The careful burial of a man, at about the same time, decorated with ochre strongly suggests that those who grieved had the concept of an afterlife. Exciting recent finds in northern Australia carry implications for our understanding of the spread of humans around the globe, but also pose some more immediate questions (Clarkson et al. 2017). If humans have been in Australia for 65,000 years, why is there no evidence for their spread to the Lake Mungo region over the following 15,000 or so years? Perhaps the Lake Mungo people just took a long way round or the time gap is simply due to too few archaeologists searching too large an area. If you go to Lake Mungo – now dry for several thousand years – and stand on the old lakebed, you can gaze up at the huge sand dunes on its eastern shore. You are now looking at the so-called ‘Walls of China’. The dunes are called lunettes and they are on the move. The prevailing wind is picking them up, sand grain by sand grain, and shifting them further east. As the top of the dune drifts away it uncovers a few old and twisted long-dead trees, stone tools and old fireplaces, all that remains of an ancient Aboriginal community. As you stand there, you will experience a silence broken only by the soughing of the wind and the hissing of the sand. For a European it is a numinous experience, akin to standing in the nave of a great cathedral. A conservative estimate suggests that the site may have been occupied for 50,000 years. There are two important discoveries of early humans at Mungo. Lake Mungo 1 includes the earliest evidence, 40,000 years old, of a cremation. The bones are those of a woman, who has now been returned to her people. A second skeleton, Lake Mungo 3, an unusually tall and slim man, had been buried on his back with his hands folded over his abdomen. Controversy surrounded his geological age, but it is now accepted that he was more or less contemporaneous with the cremated woman. 166 11. iNHeriTiNG THe earTH Good stone for the manufacture of tools is scarce in the area, and most of that worked by the Lake Mungo people has been imported from elsewhere. Points, knives, hand axes and grindstones have been recovered. The grindstones served the same purpose as the mortars and pestles used in kitchens of today: they are large and flat, with a circular, shallow bowl worn into one surface by the continuous pounding and grinding of seeds and other plant material with a rounded stone reserved for the purpose.
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