Evolutionary and Geological Time Lines • Evolutionary and Geological Timelines is a table showing important changes in the evolution of earth. • Tree of Life diagram shows relationship of major groups • Family Trees • Vertebrate Family Tree • Mammalian Family Tree • See Also: Transformation and diversification in early mammal evolution • Primate Family Tree
Hominin Family Tree • Milestones in Human Evolutionary History Buss Table 1.1 • The Hominidae family of primates whose members are known as hominids, including humans, chimpanzees, gorillas, and orangutans i.e. “the great apes”. • Homininae is a subfamily of Hominidaewhose members are known asHominins : includes Ardipithicus, Australopithecines, Paranthopus groupings and the genus homo (humans and close extinct human relatives) • Originally considered to have good upright walking • Although Ardipithecus ramidus was an early example of bipedalism and also had good climbing capabilities • Homo (genus) is the genus that includes modern humans and their close extinct relatives. • Hominins family tree and timeline • PBS Origins of Humankind • Location of Hominin fossils in Africa
How many Hominin Species? • Shattered Ancestry: Evolution of Bipedalism • 4.4-million-year-old skeleton of Ardipithecus ramidus • has characteristics of hominins and early apes (hominids) • not as much like a chimpanzee • some characteristics of arboreal and bipedal locomotion • Burtele animal foot partial bipedalism 3.4 million years ago • Australopithecus afarensis Lucy was bipedal had long arms and apelike shoulders 3.6 million to 2.9 million years ago • Bushy evolutionary tree • Several human ancestors in the same time period • Homo genus: H. erectus, H. neanderthalensis and H. sapiens overlapped in time and space
Homo Neanderthalensis • Lived in Europe and Southwestern Asia • 138,000 to 28,000 years ago • Mostly an Ice Age • Never numbered more than 100,000 • 1st Neanderthal skulls discovered in 1856, Neander Valley, Germany • Homo sapiens did not evolve from Neanderthals • 465,000 – 600,000 years ago H. Antecessor and H. Heidelbergensis were common ancestor • some evidence of interbreeding between H. Neanderthal and H. Sapiens • See "Shattered Ancestry: " p.46-47
Changes in Anatomy • Bipedalism • Requires anatomical adaptations for walking upright • Including pelvis, leg bones, foot bones, position of skull • Requires neurological adaptations for walking behavior • Role of environmental change "The Savanna Hypothesis" • Fossil evidence for evolution of bipedalism • Ardipithecus ramidus (4.4 MYA) may have been bipedal • Australopithecus anamensis (4.2 MYA) probably was bipedal • Australopithecus afarensis (3.6 MYA) was bipedal, "Lucy" example • New Bone Suggests Lucy Walked Like Us • Larynx- Voice Box • houses the vocal cords which increased range of sounds making speech possible
Changes in Anatomy • Jaws and Teeth • Teeth can be used as a weapon and for biting and chewing food • Shape and size of jaws and teeth "dentition" indicates type of food eaten • Early apes had large complex molars for grinding up vegetation and large canines as weapons • Ardipithecus ramidus 4.4-MYA had reduced canines • Australopithecus afarensis (3.6 MYA) with robust jaws and large molars • H. ergaster (1.9 - 1.8 MYA) has smaller teeth • eating small or soft food • collecting food "foraging" was assisted by use of tools
Changes in Anatomy • Hands- Opposable Thumb • Ardipithecus ramidus 4.4-MYA fingers were relatively long and curved • adapted for climbing trees • Australopithecus afarensis (2 - 3 MYA) • have a human-like pattern in the metacarpals consistent with forceful opposition of the thumb and fingers typically adopted during tool use. • See: Human-like hand use in Australopithecus africanus • Via a series of intermediate stages human thumb became fully opposable • Homo habilis (2.5 - 1.5 MYA) • Homo erectus (1.8 - 0.04 MYA) • Homo Sapien "modern" (0.20 - present MYA) • Useful for using tools to smash open bones • Useful for making tools by producing flint flakes
Changes in Anatomy • Shape and size of the skull correlates with brain size • Skull and brain size changes with hominin evolution • A. afarensis 400 cc • Homo habilis 750 cc • early Homo erectus 900 cc • later Homo erectus 1100-1200 cc • early Homo sapiens 1200 cc • Neanderthal 1500 cc • Modern Humans 1400 cc • Change in size over time appears to be gradual however it is more like a ratchet i.e. stair step • Human cognitive ability is not just because of brain size • Primates in general and humans in particular have a large brain compared to body size • Primates also have more neurons per brain size • Some areas of the brain increase in size more then others • neocortex in primates • frontal and temporal cortex areas in humans • Specialized brain circuits for face recognition, language and subjective sense of self
Changes in Anatomy • Combination of changes in specific anatomy are interconnected • Bipedalism, Small Teeth and Large Brains Timeline • a gradual change in the overall anatomy of the hominin • requisite change in behavior, cognition and brain circuits • How would behavior and cognition change with regard to these anatomical changes? • How is the concept of psychological adaptations related to these changes?
Migration • What is Migration? • movement of individuals • movement of genotypes • movement of a gene pool (gene flow) • movement of culture • Out of Africa: • H. erectus • Dmanisi Georgia site 1.77 MYA • China and Java (1.66 - 1.77 MYA) • H. antecessor (0.8 MYA) in Spain • H. heidelbergensis (0.6 MYA) in Europe • H. neanderthalensis descended from Homo heidelbergensis in Europe • H. sapiens in Europe and Asia • exodus from Africa beginning around 80,000 to 100,000 years ago • Migration Animation click on human origins then migration
Role of Migration in Human Evolution • Human Skin on the Move • The earliest members of Homo sapiens, or modern humans, evolved in Africa between 120,000 and 100,000 years ago • they had darkly pigmented skin adapted to the conditions of UV radiation that existed near the equator • Dark skinned people living in the tropics generally receive sufficient UV radiation to make vitamin D • Outside the tropics where there is less UV radiation so migrants to northern latitudes would not make sufficient vitamin D • individuals with mutations for less skin pigmentation would have more vitamin D and still be protected from UV damage
Role of Migration in Human Evolution • From Hirsute to Hairless • Hominins gradually evolved skin with less hair • Homo erectus and Homo sapiens were very active so overheating would be a problem • Chimpanzees’skin is light in color and is mostly covered by hair • The evolution of skin pigmentation is linked with that of hairlessness • Originally proposed that darker skins evolved to protect against skin cancer
Role of Migration in Human Evolution • Built-in Sunscreen • skin contains cells called melanocytes that are capable of synthesizing the dark-brown pigment melanin in response to exposure to UV radiation • However, most skin cancers occur later in life after the first reproductive years • not enough evolutionary pressure for cancer protection alone to account for darker skin colors • The Folate Connection • Light-skinned people who had been exposed to strong sunlight had abnormally low levels of the essential B vitamin folate in their blood • Folate deficiency in pregnant women is related to an increased risk of neural tube defects such as spina bifida • Protection from birth defects would be a strong selection factor for darker skin
Tools as part of Culture • Earliest examples of culture in Hominins • A. afarensis ~ 3.5 MYA primitive stone tools? • A. africanus ~ 3.0 MYA primitive stone tools? • H. habilis - 2.5 MYA primitive stone tools • Homo habilis 2.5 MYA at Olduvai Gorge selective in choosing particular rock materials • Oldowan tools core tools most likely functioned as multipurpose hammering, chopping, and digging implements • flake tools were used without further modification as knives • Homo erectus tool use • 1.7-1.6 MYA using advanced Oldowan • 1.5 MYA using Acheulian hand axe multipurpose implements used for light chopping of wood, digging up roots and bulbs, butchering animals, and cracking nuts and bones • Late transitional Homo erectus using softer hammers for greater control in the final shaping process • progressive improvement in tool making over time • reliance on tools increased as the implements became more useful • What psychological adaptations are needed for tool use and tool making?
Tools as part of Culture • Homo sapiens, Homo heidelbergensis or Homo neanderthalensis • Mousterian tool tradition in area of "France" • specialized flake tools "Levallois" became more common • flake scraping, cutting, puncturing implements and spear points • Tool Invention • How does this differ from tool use? • Who came up with the idea for a new tool? • Why did a new invention spread across a population? • see Stone toolmaking and the evolution of human culture and cognition
What role does culture play in the evolution of hominins? • How does the accumulation of culture change the selection pressures for Hominins? • New food getting techniques • australopithecines were primarily wild plant food collectors occasional scavengers of meat and eggs • Homo erectus used hunting, carcass scavenging and harvesting vast amounts of wild plant foods • expanding range of Homo erectus with migration out of Africa • evidence of cooking 780,000 and 400,000 years ago • Controlled use of fire 400,000 - 300,000 years ago • Biocultural Evolution: • use of culture for survival • "tools" becomes so common that culture becomes part of the environment • because the environment exerts selection pressure culture becomes part of the selection pressure