Story of our ancestors

Question 1

What are the main characteristics of hominin evolution?

Answer 1

• clodgenesis: ramification and dead-ends on phylogenetic tree (opposite to anagenesis, which is the gradual evolution in a straight line)
• apomorphism: derived characteristics
• plesiomorpic traits: ancestral traits

Question 2

Why did bipedalism evolve?

Answer 2

Bipedalism is the ability to walk up-right, on two feet, and it must have been extremely beneficial, since humans are not the only species to have evolve it:

• freed the hands to transport food
• enhance overview of the surrounding to easily spot predators
• very efficient way of moving forward
• reduce the amount of absorbed solar radiation

Question 3

Why is it said that there’s a mosaic evolution in A. afarensis?

Answer 3

In “Lucy” we can see the perfect example of mosaic evolution: she has both old traits (apomorphism) and new traits (plesiomorphism).
Mosaic evolution demonstrate how human traits didn’t evolve all at the same time, but there were transitional states in which old and new traits were present.

Question 4

Why Homo erectus is believed to have migrated? What are the two thesis that support this opinion?

Answer 4

Homo erectus is the first hominidae species to migrate outside of Africa. Fossil records show various H. erectus throughout the world:
- Java man
- Peking man
- H. gorgicus
- H. antecessor
- H. naledi
All these species have been divided (splitting theory) because of their diversities in both morphology and geographical area, but it may have been simple genetic variation of the H. erectus, who migrated (lumping theory).

Question 5

What is a species?

Answer 5

1. Group of organisms that can produce fertile offsprings.
2. DNA sequence similarity.
3. Similar behaviour
4. Same ecological niche
5. Morphology

Question 6

What are the different modes of speciation?

Answer 6

Speciation is the process of reproductive isolation followed by local adaptation or genetic drift over time.

1. Sympatric speciation: evolution occurred in the same place.
2. Allopatric speciation: a subpopulation left the main group and colonized a new area.
3. Parapatric speciation: new species evolve in contiguous, yet spatially segregated habitats.