1859 was a crucial year for our understanding of living organisms and how they came into their present form. This was the year in which Charles Darwin published The Origin of Species’. He did not, however, discuss the descent of humans in his book. Fossils of many ancient creatures had been already recognised as such, but human fossils, such as the ones found in a cave burial at Paviland in Wales in 1822 (subsequently dated to 30,000 years ago) were thought to be Roman. The principles of evolution set forth in the book could obviously be applied to humans but Darwin could find no evidence.
The problem in the early days of palaeontology was that there was no way of actually dating the fossils which had been found. It was not until the 1950′s with the development of carbon dating that sophisticated dating methods became common and the placement of fossils in a time frame became possible. Over the last 150 years the principles of evolution proposed by Darwin, plus these methods, have allowed some grasp of our origins although the lines of descent are by no means clear. Many more hominid fossils need to be discovered before this is possible.
It is now understood that we evolved in Africa. In a period of climate change about 6 million years ago, one group of apes adopted an adaptive strategy which eventually led to modern humans. The first adaptation towards the human form was bipedalism. The reasons for this are not very clear but fossils of the period 3.5 to 3 million years ago show that proto humans now walked upright. More dramatically, in the 1950′s, Mary Leakey, who was excavating at Laetoli in the Olduvai Gorge, uncovered a set of footprints which showed that three people, one a child, had walked across a stretch of mud and these had become fossilised. They were later dated to 3.2 million years ago.
Olduvai Gorge, Tanzania
Once a mammal species has become established it is common for that species to radiate to fill all of the appropriate niches in a particular environment. It is thought that there may have been as many as sixteen separate species of proto humans at this point and this adds to the difficulty of tracing a line of descent. It is only possible here, to discuss the most likely path which led from apes to humans.
A Reconstruction of Australopithecus Afarensis
The earliest species to show bipedalism were the Australopithecines. They walked upright and they were the first to MAKE stone tools (rather than use stones which they found in the landscape). This happened about 3 million years ago. Again in the Olduvai Gorge in the 1950′s, the Leakeys unearthed another major species, the Homo habilines, so called ‘Handy Men’ because of the more sophisticated tools found at this site. Homo habilis also showed a brain size beyond that of apes, ape brains being around 300/400 cubic millilitres, the Homo habilenes brain being 750 cubic millilitres. It is now clear that they were not in the ‘Man the Hunter’ mode as proposed by many writers in the 20th century. Small and puny they lived by eating nuts, seeds, roots and insects with occasional opportunistic scavenging. Homo erectus was the next major species and they evolved about 2 million years ago. This was a different creature. Much taller, with a brain capacity of 850/1100 cubic millilitres, they are the species acknowledged by most workers to be the ones directly ancestral to modern human beings.
They spread out of Africa and their fossils and tools are found in places as widespread as Java, China, Damanisi in Georgia, Ceprano in Italy, Once in Spain and in Britain. At Happisburgh in Norfolk where both tools and faunal remains with butchery marks have been found dating to perhaps 700,000 years ago and certainly before 500,000 years ago. This was a tropical period marked by the remains of elephants, hippos, bears hyena, wolves, lions and sabre toothed cats. Sites similar to this can be found at Pakefield and Norton-sub-Course both in Norfolk, and Westbury-le-Mendip in Wiltshire.
The most famous site is at Boxgrove in Sussex where, in 1995, a human thighbone was found. This was dated to about 500,000 years ago and at that time was the oldest human fossil in Europe. More locally still, we have evidence of these periods at Pengelly Cave in Buckfastleigh where the excavated faunal remains cover a long time span dating to both these warmer periods and the glaciations which punctuated them. Similar evidence can be found at both the Brixham Bone Cavern and Kents Cavern in Torquay. This last is known for its association with Neanderthals but at the last excavation there by the University of Oregon, indicated that a similar site to that at Boxgrove could lie in the unexcavated areas.
The descendants of these people evolved into the European species, the Neanderthals, whose altered physique was a response to the continuing ice ages which intermittently spread across Europe. Neanderthal sites in Britain are at Pontnewydd Cave in Wales and of course, Kents Cavern. After nearly 2 million years of existence, Homo erectus began to evolve into the large brained species Homo sapiens sapiens. In other words US. This happened in Africa about 300,000 years ago but they again spread out of Africa as their forebears had. At 200,000 years ago, we were found living in caves in Israel. We then moved along coasts until we had colonised Asia and by 50,000 years ago, we had moved into Australia. The Asian migrants turned north and avoiding the huge mountain ranges of central Asia occupied southern Russia and the Balkans. Unlike their ancestors, Homo erectus who were a tropical species, these people had devised ways of living in hostile environments. Some turned west and came into Europe arriving as Cro Magnons (after the place where they were first identified) about 30,000 years ago. Their living spaces are to be found in Cresswell Crags in Derbyshire, Gough’s Cave in Cheddar and again Kents Cavern.
It is due to Darwin that we can understand the connections between of these species. Given their very different appearance, behaviour and life ways, in a different era we would have considered them separate creations rather than closely connected to each other. It was Darwin who gave us the theories by which we can understand how these connections came into existence.