Chapter 2

Question 1

How do you estimate relative brain size?

Answer 1

1. Compare brain size to body size (encephalisation quotient EQ)
2. Count brain cells

Question 2

Why is the hominin brain enlarged?

Answer 2

1. Drastic climate changes like deserts due to the Great Rift Valley lead hominins to adapt and lead more complex food finding/handling behaviours.
2. Primate lifestyle of sociality favors a complex nervous system
3. Brain growth is linked to brain cooling
4. Slow maturation rate favours larger brains

Question 3

What is phenotypic plasticity?

Answer 3

Phenotypic variation due to environment, expression, age etc.

Question 4

What causes phenotypic plasticity?

Answer 4

It begins with cell division in the developing embryo where gene expression is influenced by factors inside and outside the cell (may explain no 100% concordance between twins). Epigenetics then play a role such as with methylation where a methyl group attaches to the DNA nucleotide base pair sequence which decreases or increases gene expression. Epigenetic changes can also be inherited. Experience during a critical period of development ca also modify genes.