Life on Earth Evidence for human evolution

Evidence for human evolution Image details Chimpanzee looking thoughtful. (Tom Brakefield/ Corbis UK Ltd.) Mountain Gorilla. (Oxford University Press) Chimps and gorillas are apes. Human beings share many features with them. Chimps and gorillas are our closest living relatives.

Evidence for human evolution Feature Gorillas Human beings Chimpanzees Chromosomes Head hair Calf muscle Buttocks Arms vs legs Canine teeth Thumbs short small thin shorter legs large long 48 shorter arms 46 fat From this evidence, do you think human beings are closest to chimps or gorillas?

Evidence for human evolution It’s not a trick question! human beings chimps or gorillas? So far we haven’t found enough evidence to decide. But there is enough evidence to say that humans and apes share the same ancestor.

Evidence for human evolution We know that ape-like animals were living in Africa over 20 m y a. The evidence: scientists have found skulls with ape-like features Image details SOMSO Model of Proconsul africanus skull. (Marcus Sommer - SOMSO MODELLE) they can date the fossils

Evidence for human evolution These early apes share some features with living apes: no tail shoulder blades at the back of the body Image details SOMSO Model of Proconsul africanus skull. (Marcus Sommer - SOMSO MODELLE) But they also have some differences.

Evidence for human evolution Scientists use the evidence to work out how living apes are related to fossil apes. fossils gibbons orangutangs chimpanzees and gorillas human beings

Evidence for human evolution Do human beings have any closer relatives in the fossils? chimpanzees and gorillas ? human beings

Evidence for human evolution Australopithecines lived in Africa 1.5 to 4 m y a. Lucy - the most complete Australopithecine skeleton found. Image details Fossil hominid skeleton Australopithecus afarensis known as 'Lucy' (AL 288-1). Lucy was part of a rich find of fossils made in the Afar region of Ethiopia between 1973 & 1977. She dates from 3.3 million years ago & is widely accepted as the earliest link in the human record. The remains comprise 40% of the entire skeleton and include skull fragments, a mandible, most of the left & right arm, vertebrae, rib fragments, sacrum, left pelvic bone, left thigh & right lower leg. The form of the pelvic bones showed her to be female, erupted wisdom teeth suggested she was 20 years old & the thighbone indicated she was small, between 107 and 122 centimetres (4 feet) tall. (John Reader/ Science Photo Library) So is Lucy more closely related to us or to living apes?

Evidence for human evolution jaw more like human than chimpanzee sinus (spaces inside skull) eye socket broad nose modern human A. africanus chimpanzee Australopithecines share some features with human beings. eye sockets are wide and set apart broad nose sinus inside front of skull

Evidence for human evolution jaw more like human than chimpanzee sinus (spaces inside skull) eye socket broad nose modern human A. africanus chimpanzee Chimps and gorillas also have these features. But other apes don’t. So are Australopithecines more closely related to: (a) human beings? or (b) chimps and gorillas?

C9 Evidence for human evolution In 1978 scientists found the evidence to answer this question. These footprints were made in Africa by Australopithecines. They walked on two legs. Image details Trail of hominid footprints fossilized in volcanic ash. This 70 metre trail was found by Mary Leakey's expedition at Laetoli, Tanzania in 1978. It dates from 3.6 million years & shows that hominids had acquired the upright, bipedal, free-striding gait of modern man by this date. The trail probably belongs to Australopithecus afarensis & dates from 3.7 to 3.0 million years ago. The footprints show a well developed arch to the foot & no divergence of the big toe. They are of two adults with possibly a third set belonging to a child who walked in the footsteps of one of the adults. (John Reader/Science Photo Library)

Evidence for human evolution So Australopithecines were more like human beings than chimps and gorillas. chimpanzees and gorillas australopithecines human beings

Evidence for human evolution But scientists think that we have even closer fossil relatives. Habilines lived in Africa 1.6 to 2 m y a. Fossils show that their spines were joined to the middle of their skull, so habilines walked upright. Image details Artwork of a male Homo habilis sitting on a rock whilst making a stone tool. Homo habilis lived 2.0-1.6 million years ago and had a wide distribution in Africa. The term Homo habilis means "handy human" and it refers to the fact that H.habilis was very adept at making and using tools. These tools would be carved out of stones and animal bones. Unlike Australopithecus afarensis, its predecessor, H.habilis was a meat-eater. This has been deduced from teeth conformation found in the skulls of that period. It is thought that Homo habilis was the first truly human species on Earth. (Christian Jegou, Publiphoto Diffusion/ Science Photo Library).

Evidence for human evolution Species Brain size (ml) Human beings Australopithecines Habilines 1400 500 650 We have more evidence about habilines. They had much bigger brains than Australopithecines like Lucy. We also know that they made tools. So the evidence tells us that habilines are more closely related to modern humans than Australopithecines.

Evidence for human evolution australopithecines habilines human beings Habilines were probably the first animals on earth to make tools. Tool making is a very important feature of human beings. So scientists think habilines were the first early humans. They are called Homo habilis.

Evidence for human evolution Species Brain size (ml) Human beings 1400 Australopithecines 500 Habilines 650 Homo erectus 900 Fossils of other early humans have also been found. Homo erectus lived in Africa 1.5 m y a.

Evidence for human evolution habilines (Homo habilis) Homo erectus modern humans Their large brains mean that Homo erectus are more closely related to modern humans. Scientists have also found evidence that they were able to make fire.

Evidence for human evolution Homo erectus were also the first early humans to leave Africa. Their skeletons have been found in Asia and Europe.

Evidence for human evolution But Homo erectus are not quite the same as modern humans. For example, their skulls have a thick, straight brow ridge. So scientists think that we must have at least one more recent ancestor.

Evidence for human evolution The search goes back to Africa. We know that not all Homo erectus left when they first moved out of Africa. Those that stayed carried on evolving into modern humans. We know this because skulls shaped more like a modern human have been found in Africa. This one from Ethiopia is only 160,000 years old.

Evidence for human evolution Modern humans are called Homo sapiens. habilines Homo erectus modern humans They left Africa about 120,000 years ago. Homo sapiens fossils this old have been found in Israel.

Evidence for human evolution By 40,000 years ago modern humans had spread across the world. Evidence like cave paintings and tools tell us where and how they lived. Image details Detail of animals from a Paleolithic mural painting series in Lascaux. (Pierre Vauthey, Sygma/ Corbis UK Ltd.)

Evidence for human evolution Image details Artwork of an early modern human Homo sapiens teaching his two sons how to make stone tools. In the background, at far left, men are using spears to catch fish. Homo sapiens first appeared around 90,000 years ago towards the end of the Paleolithic era (750,000-15 000 years ago). Early Homo sapiens made many specialized tools, spears and needles. By about 10,000 years ago agricultural villages started to develop. This marked the start of the Neolithic period or new stone age. (Christian Jegou, Publiphoto Diffusion/ Science Photo Library) These modern humans were hunters and farmers. The symbols in their paintings tell us that they had language. They also had ceremonies like burials.

Evidence for human evolution modern humans early humans Australopithecines living apes, like chimps and gorillas Summary: Different groups of humans evolved from a common ancestor. All but one of these groups died out. Only Homo sapiens (modern humans) survived. Modern humans evolved in Africa.