Session 2: Human Evolution Flashcards
What are human characteristics?
larger brains, increased intelligence, teeth changes, loss of body hair, and bipedalism (we have legs, etc.)
What features were needed for the evolutionary step of bipedalism?
forward-pointing big toe and the evolution of a foot to be less like a grasping hand, transverse arch in the spine to absorb impact, foramen magnum (connects the spine to the brain) at the central base of the skull instead of towards the back of the skull, angle of the femur that allows us to stand easier, strong knee joint, lower & broader pelvis, and strong gluteal muscles. Humans are the only habitual bipedal primates, and several adaptations were needed for this evolutionary step.
What encouraged the selection for bipedalism?
The need for: higher vision (ability to see over grasslands), holding tools, weapons, food, offspring, etc. in hands, locomotion (leg movement more efficient for long-distance walking), thermoregulation (less exposure to the sun, better cooling via evaporation). Habitat changed and it went from thick forest to wooded savannah that made the changes necessary.
What were the primitive features of “Lucy”? (Australopithecus afarensis)
“Lucy” was one of the earliest known bipedal hominins, her skeleton had features consistent with a species adapted for walking bipedally, but it also had many “primitive” features normally associated with arboreal existence (living in trees). The features were: bipedal, walked erect but also arboreal, human-like hands and teeth, brain capacity of about 375-550 cc (cubic cm) (modern humans have about 1350 cc), apelike face with sloping forehead, distinct ridge over the eyes, flat nose and chinless lower jaw, between 1 and 1.5 m tall.
What is Genus Paranthropus?
Paranthropus were a group of species that ate low-grade vegetable food sources (nuts, root tubers and seeds) resulting in (megadont) species with very large teeth and jaw (this was their defining feature). Initially classified as Australopithecines (human ancestors), it is now thought they were descendants of that group but none of these species is considered to be a direct ancestor of humans.
What are the features of homo erectus?
2 mya - 400 000 ya, Early examples had a 850cc brain size, which increased to 1100cc, The species definitely had communication of some sort (enlarged Broca’s and Wernicke’s areas of the brains which are for speech production and speech recognition, and structure of jaw & throat), H. erectus developed tools, weapons and fire and learned to cook food, Face had massive jaws with huge molars, no chin, thick brow ridges, and a long low skull - but the ability to now cook food led to these features changing, e.g. teeth getting smaller. Sturdier in build and much stronger than the modern human.
What were the adaptations for running?
Loss of hair, sweat for cooling, high SA:V, Elongated legs, Nuchal ligament (back of neck) stabilises head, Thickened joint surfaces in knees and other high impact joints, Plantar arch in foot acts as a spring, Achilles tendon, Well developed gluteus maximus, More muscles attached to the lower spine for support.
What were the reasons for the selection of reduced body hair?
Parasite control, retention of head hair to reflect and radiate solar radiation, and thermoregulation (sweat glands, etc.) Main reason was sweating. This all happened because they began to live in one location for long periods of time.
Describe the evolution of the human brain.
Intelligence is not just a function of brain size: relative brain size appears to be more important (brain size compared to body size). Another important factor is the organization of the brain, evident in the development of the areas concerned with spoken language. Two areas of the brain have become highly developed in modern humans: Broca’s area concerned with speech, Wernicke’s area concerned with comprehension of language.
What are the last two hominins?
Homo neanderthalensis (Europe) and homo sapiens.
What are the features of homo sapiens (also called cro-magnon)?
Homo sapiens evolved in Africa - better suited for a hot climate, Moved into Europe approximately
90,000 ya, Brain is around 1400cc with a high frontal lobe/forehead,
The first anatomically modern humans appear possibly as early as 300,000 years ago in Africa and the Middle East. They underwent a sudden cultural revolution about 40,000 years ago, with the appearance of Cro-Magnon culture. Using a wider range of materials, their tool kits became markedly more sophisticated. They were skilled hunters, tool-makers
and artists (cave art and music).
Hominids vs Primates vs Hominins:
Hominids: all modern and extinct great apes: humans, chimpanzees, gorillas, etc. no tail, different posture to primates, large brain, etc.
Primates: things like lemurs, monkeys, etc. tree-dwelling, grasping hands and feet, etc.
Hominins: human species
What were the three main ancestors of humans (and what order was it)?
Homo habilis –> Homo ergaster –> Homo erectus
Homo neanderthalas came after homo erectus, it’s believed that Homo sapiens and homo neanderthalas interacted.
