Module 7

Question 1

Mans postion in the tree?

Answer 1

Primates -> Anthropoids/simians -> Hominoides -> Hominids -> Hominins

Question 2

Overview of the traits of humans and extant hominids?

Answer 2

The following are some dissimilarities:

• Lack of body hair
• Brain
• Face
• Neck
• Hip
• Backbone
• Hand
• Leg
• Foot
• Eccrine sweat glands

The brain has higher EQ and Broca’s and Wernicke’s area for language and speech. The face is flat, marked chin, distinct nose, foramen magnum, and small canine teeth. The hand provides a mobile thumb, and the arched feet have adapted to bipedal walking with a stronger Achilles tendon but cannot grip as hard. Arched provides stiffness and acts as a lever that transmits forces when the muscles push against the ground, and flexibility like a spring that store and release mechanical energy. The legs are long with stronger muscles for bipedal walking. The spine is S-shaped and a wider pelvis. Less body hair and eccrine glands for cooling. All in all, to provide:

Upright walking – Handiness – Intelligence – Endurance running – Persistence hunting.

Question 3

In which order did the brain, bipedalism and handiness evolved?

Answer 3

Few findings of pre-historic humans, but two hypotheses for behaviorally modern humans:
The great leap forward: A sudden burst of creativity possibly due to change in mental capacity – hardware change.

The continuity hypothesis: A gradual accumulation of knowledge and language development that finally enabled fully abstract thinking and greater creativity – software development.
Early researchers hypothesized that brain enlargement was the first hallmark of the hominin lineage. In the mid-1800s until the early 1900s, almost all known fossil hominins had relatively large brains. The large brain hypothesis was falsified after the discovery of early hominin fossils exhibiting ape-sized brains and bipedally-adapted morphology in 1924. Raymond Dart identified the first australopith fossil, the Taung Child, in South Africa, which belonged to the Au. africanus and had a relatively small brain equal to the size of modern chimpanzees. The placement of the foramen magnum also suggested that the Taung Child was bipedal. Dar hypothesized that bipedalism evolved before larger brains, not consistent with the scientific reasoning at the time. Because of his small sample size and the fragmentary remains, debate about the timing of bipedalism and brain size continued for the next 50 years.

The finding of LUCY (3.7-2.9 MYA) in 1974 changed everything when Donald Johanson found the nearly complete fossilized skeleton, a member of the Au. afarensis (3.2 MYA), the first fossil to exhibit small brain size and bipedalism. Older fossils (7 MYA) found later resulted in a revision of the bipedalism timeline. The evidence demonstrates that bipedalism was one of the first hallmarks of the hominin lineage and may have led to many more advances. One advantage of bipedalism is that the hands are relieved and allowed to produce advanced stone tools for hunting. A higher protein diet may have affected the brain size. Other changes are due to lower expression of the genes for some traits – the genetic makeup is still there but does not express.

Question 4

Primates?

Answer 4

Master or ruling order within the mammal class – a clad that includes all extant and extinct species descending from the recent ancestor to apes, monkeys, tarsiers, lemurs, lorisids.

Question 5

Hominid?

Answer 5

A family within primates that represents a clad with extant and extinct species that are descendants from the most recent common ancestor to humans, gorilla, chimpanzees, and orangutan.

Question 6

Hominin?

Answer 6

Subfamily with extinct and extant species that are descendants from the most recent common ancestor to humans – after the split from great apes.

Question 7

Life history that differs?

Answer 7

Compared to other primates and mammals, there are at least three distinctive characteristics of human life histories: (1) an exceptionally long life span, (2) an extended period of juvenile dependence, and (3) support of reproduction by older postreproductive individuals.

The logic underlying this proposal is that for humans, effective adult foraging requires an extended developmental period during which production at young ages is sacrificed for increased productivity later in life. The returns to investment in development depend positively on adult survival rates, favoring increased investment in mortality reduction. An extended postreproductive, yet productive, period supports both earlier onset of reproduction by next-generation individuals and the ability to provision multiple dependent young at different stages of development.

Two major tradeoffs were considered. First, resources can be invested in either current or future reproductive effort. Investments in future reproductive effort include both those that enhance survival and increase future income (in a general sense). Age-specific allocations that maximize the lifetime allocation to reproductive effort will be favored by natural selection. Second, there is a tradeoff between quantity and quality of offspring. The specific model of human life-history evolution proposes that compared to other primates, traditional human ecology favored higher levels of investment in both future reproduction and quality of offspring.

Does it take 20 years to learn how to hunt and gathering? Social abilities

Menopause - providing an increase in fitness on a group level - incerase fertility among the daughters.