Life on Earth

1. Life on Earth Evidence for human evolution

2. Evidence for human evolution • Chimps and gorillas are apes. • Human beings share many features with them. • Chimps and gorillas are our closest living relatives.

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

4. human beings chimps or gorillas? chimps or gorillas? Evidence for human evolution • It’s not a trick question! • 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.

5. 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 • they can date the fossils

6. Evidence for human evolution • These early apes share some features with living apes: • no tail • shoulder blades at the back of the body • But they also have some differences.

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

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

9. Evidence for human evolution • Australopithecines lived in Africa 1.5 to 4 m y a. • Lucy - the most complete Australopithecine skeleton found. • So is Lucy more closely related to us or to living apes?

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

11. sinus (spaces inside skull) eye socket broad nose jaw more like human than chimpanzee modern human A. africanus chimpanzee Evidence for human evolution • 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?

12. 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.

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

14. 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.

15. Species Brain size (ml) Human beings 1400 Australopithecines 500 Habilines 650 Evidence for human evolution • 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.

16. human beings habilines australopithecines Evidence for human evolution • 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.

17. 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.

18. modern humans Homo erectus habilines (Homo habilis) Evidence for human evolution • 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.

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

20. 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.

21. 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.

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

23. 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.

24. Evidence for human evolution • These modern humans were hunters and farmers. • The symbols in their paintings tell us that they had language. • They also had ceremonies like burials.

25. modern humans early humans Australopithecines Summary: living apes, like chimps and gorillas • 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. Evidence for human evolution