Answer sheet for “Three Lice” Activity Catherine Leal
Although you will be working in small groups, be sure to answer all questions in your own words
List two
possible hypotheses for why human head lice diverged evolutionarily from chimpanzee
lice:
One possible hypothesis is that as humans evolved and lost body hair so the lice had to adapt, which caused a diversion among lice.
Another possible hypothesis is due to humans evolving to wearing clothes and living in a different environment than chimpanzees.
Q 1: What would you predict, given the co-speciation hypothesis? The last common ancestor of chimp lice and human head lice lived approximately:
A.
20 million years ago, on an early ape ancestor.
B.
6 million years ago, when ancestral chimps and hominins diverged.
C.
100,000 years ago, on an early human.
List at least one possible hypothesis for why human head lice diverged evolutionarily from human pubic lice:
Pubic hair and hair on your head are different, thus the lice would have to adapt two the different hair types.
Also, the pubic area is covered mostly making it a darker and warmer environment than one’s head.
Q 2: What would you predict, given the new niche hypothesis? Human head and pubic lice lineages diverged from a common ancestor approximately:
A.
25 million years ago, when ape and monkey lineages split.
B.
6 million years ago, when human and chimp lineages split.
C.
6 million years ago or less, on a hominin host.
Q 3: Why do we conclude that human head and pubic lice did not diverge on a hominin?
A.
Human head and pubic lice lineages diverged well before hominins evolved ~6 million years ago.
B.
Humans had body hair well after 12 million years ago.
C.
The fossil record does not show pubic lice on people that long ago.
Q 4: Given the phylogeny of select primates and their lice, what is the most likely origin of human pubic lice?
A.
Human pubic lice are most closely related to chimp lice.
