Hominin Evolution

1. Hominin Evolution Chapter 15 – Part 2

2. Hominin Species: When Did They Live? • The oldest hominin fossil that has been found would have lived between 6-7 million years ago. • Early hominins shared some of the derived characteristics of humans. • E.g.: they had reduced canine teeth, and some fossils suggest that they had relatively flat faces. They also show signs of having been more upright and bipedal than other apes. • One clue to their upright stance can be found in the foramen magnum, the hole at the base of the skull through which the spinal cord exits. • In chimpanzees, the foramen magnum is relatively far back on the skull, in early hominins (and in humans), it is located underneath the skull. • This position allows us to hold our head directly over our body.

4. The Australopithecines • The fossil record indicates that hominin diversity increased dramatically between 4 million and 2 million years ago. • Many of the hominins from this period are collectively called Australopiths.

5. The Australopithecines • There appear to have been several species of Australopithecus. • Some of these are likely to have been in the human line. • There are two general types of Australopithecines: • Robusts • Graciles

6. Homo habilis 1.5 mya RobustAustralopithicus extinct Australopithecus africanus 2 mya Australopithecus afarensis 4 mya

7. The Robust Australopithecines • The robust Australopithecines3 – 1.5 mya • Australopithecus aethiopicus • Australopithecus boisei • Australopithecus robustus • Main features of the robust Australopithecines: • Brain size around 500 mL • Very large molars • Bony crest on top of the skulls of males. • Males range from 1.3-1.4 m tall and females range from 1.0-1.3 m

8. Robust Australopithecines

9. The GracileAustralopithecines • The gacileAustralopithecines were ancestral to the first Homo species • Some examples of gracileAustralopiths: • Australopithecus anamensis • Australopithecus afarensis (Lucy) • Australopithecus africanus (Taung Child) • Some of the main features of the gracileAustralopithecines include: • Brain size around 400 mL • Large molars • Rounded top skull • Males range from 1.4-1.5 m in height and the females range from 1.0-1.2 m in height

10. Lucy • Lucy is the most complete skeleton of an early hominid. • Found in Hadar, Ethiopia (1974). • Dated at 3.2 million years old • 40% of her skeleton was found. • Bipedal • Australopithecus afarensis • Found in many areas of East Africa. • 4.0 – 3.0 mya. • Lucy was a small-brained biped. • Small brain 380 – 500 mL • Lucy was 3’6” tall 50 lb • Dates to 3.2 mya

11. Sexual dimorphism in Australopiths • Australopithecus individuals displayed sexual dimorphism. • This is when the male and female of the species look different to each other. • E.g.: in the case of the Australopithecines, the males are much larger than the females.

12. Social Organisation • Social organisation amongst species determines the degree to which sexual dimorphism is displayed. • Species who form monogamous pairs show little dimorphism, whereas polygamous spices show significant differences between males and females.

13. Diets Zygomatic Arches • Studying fossilised skulls can provide us with evidence of the diet of a particular species. • For example studying the zygomatic arches , the muscles that run through them and the jaw (including teeth). • The size of the zygomatic arches indicates the size of the muscles associated with the movement of the jaw.

14. Diets • The robust Australopithecines had diets which included mainly tough and fibrous vegetable matter. • This is evidenced by • large jaws and jaw muscles • Flat, large molars provide • The gracileAustralopithecines also had a diet mainly consisting of vegetable matter, however, their smaller jaws and jaw muscles suggest that the food they ate was of a less fibrous nature.

15. Diets • As the species of Australopithecines were herbivorous, they had relatively large digestive tracts. • In order to accommodate this, they had wider rib cages and waists.

16. Habitats • The Australopithecines had various habitats, but these habitats were usually in or near forests. • A few species of Australopithecines also lived in grassland savannahs.

17. Locomotion • The Australopithecines had skeletons which were capable of bipedal locomotion. • However, they were also capable of life in trees (arboreal) as they had long digits on their hands and feet, as well as long arms for swinging in between branches. • It is thought that these hominins hunted out in open landscapes during the day and then retreated into the forest at night for shelter and protection.

18. The genus Homo • The first members of the genus Homo were found in Africa, dating back to 2.4 million years ago. • The defining features of the Homo genus were: • Reduction in size of teeth • An increase in brain size • Increase in size of the cranium (to accommodate the brain)

19. The genus Homo • There are many features associated with the genus Homo, including: • Enlargement of brain • Reduction of tooth size • Shortening of face • Making and using fire • Caring for aged and ill members • Burying the dead • Development of art • Language • Music • The use and development of technology.

20. Homo habilis: The First Toolmaker • Homo habilishad the following features: • Face is much flatter • Reduced brow ridge • Larger cranial capacity (680 mL) • Homo habilisalso used tools in order to strike things, such as nuts.

21. Homo erectus • Homo erectus evolved from Homo habilis about 2 million years ago. • It is widely believed that Homo erectus was the first species to venture out of Africa. • This is evidenced fossils of Homo erectus being found in continents out side of Africa.

22. Larger brained and smarter • The brain size of Homo erectus was between 900 and 1,000 mL. • As a result of the increased brain size (and intelligence), Homo erectus displayed some new skills: • Use of fire • Crafting of better tools • Cooperative hunting

23. The Hobbit: Homo floresiensis • In 2004, a number of fossilised remains were found in Indonesia of a new hominin species. • It has been estimated that this species existed around 18,000 years ago. • Until the discovery of these fossils it was believed that Homosapiens were the only hominin species after the Neanderthals became extinct. • The discoveries of these fossils suggest that Homo floresiensis and Homo sapiens would have existed alongside each other.

24. Homo heidelbergensis • Homo heidelbergensiswas an intermediate species between Homo erectus and Homo sapiens. • Their brain capacity is between 1,100 and 1,200 mL • The fossils that have been found have been dated between 400,000 and 40,000 years ago. • These fossils have been found on a number of continents including: • Asia • Europe • Africa

25. Homo neanderthalensis • Fossils of Neanderthals have been found all over the world. • These individuals had large brains (1,400 mL). • They were built strongly, with larger bones. • It is thought that the Neanderthals may have buried dead individuals. • They existed between 150,000 and 35,000 years ago. • This species existed at the same time as Homo sapiens and therefore they are NOT our ancestors.

26. Modern Humans: Homo sapiens • Evolved in eastern Africa. • Appeared 100,000 years ago. • Highly complex weapons and tools. • Brain capacity around 1,400 mL

27. Agriculture and the first villages • Evidence has indicated that Homo sapiens had set up agricultural farms and tended to domestic animals around 10,000 to 12,000 years ago. • This was mainly in the Middle East in what is known as the “fertile crescent” • The first plants to be cultivated were wheat, barley and pea plants.

28. Changes in human population • Changes in human populations have been driven by a number of factors, including: • Biological evolution • Cultural evolution • Technological evolution

29. Human biological evolution • Biological evolution refers to the changes in human populations that has resulted from natural selection. • This allows the population to adapt to their particular geographic area. • Some of the traits that have been selected for in different human populations include: • Physical traits: such as variation in skin colour and hair texture. • Biochemical traits: such as ABO and Rhesus blood types. • Physiological traits: such as tolerances to non-human milk, extreme temperatures, etc.

30. Climate and body shape • The climate of regions have major effects on body shape. • For example, people living in hotter areas are generally thinner and taller, those living in colder environments are shorter and wider. • This difference can be explained by comparing the surface area to volume ratio of individuals from hot and cold climates. • Individuals from hotter climates have a high surface area to volume ratio, allowing them to lose heat more rapidly when they sweat. • Individuals from colder climates have a low surface area to volume ratio, allowing them to retain heat more efficiently.

31. Human Cultural Evolution • Cultural evolution refers to any type of learned behaviour (either learned or imitated). • This can include: • Making tools • Learning to write • Learning rules in social groupings • New ideas and knowledge • Customs • Symbols • Skills • Learning to play musical instruments

32. Technological Evolution • Technological evolution refers to changes over time in technology that give humans increased control over their environment.

33. Technology extends capabilities • Humans have developed and used technology to allow us to achieve things beyond our physical capabilities. • For example: • Using glasses to see • Using various vehicles to travel • Bionic Ear

34. Biology, culture and technology interact • It is important to remember that biology, culture and technology are interrelated. • Biological evolution created larger brains in the Homo sapiens, this allowed them to develop the technology of tool use, and developed their culture so they hunted in cooperative groups.