Anthropology 005
Problem Set #6
Winter 2023
1. Biparental care, while very common in birds, is relatively rare in mammals. For example all
of our close relatives among the great apes—chimpanzees, gorillas, and orangutans—exhibit
uniparental care by the female. The relevant derived trait in the human lineage is a shift in
male reproductive effort, away from seeking additional mates and towards caring for the
offspring of one mate. Of course the behavior of males and females in the context of
reproduction should be subject to strong selection.
A. What evolutionary payoff could a male get by giving up additional mating opportunities?
By investing time and resources into caring for offspring, a male can increase the
chances of survival and reproductive success of his existing offspring, which can lead to
greater genetic representation of his offspring in future generations.
B. Why might that payoff be larger for humans than for chimps?
The payoff of caring for offspring maybe larger in humans than in chimpanzees
because human infants are born with a relatively undeveloped brain and require a longer
period of care and learning from both parents to survive and thrive.
C. Are there any bird species with uniparental care (as in the non-human great apes) and, if
so, does the distribution of uniparental care in birds support the argument you advanced in
you answer to question 1B?
Yes, there are bird species with uniparental care, such as some species of shorebirds
and some raptors. The distribution of uniparental care in birds does not support the
argument that the payoff for investing in offspring care can be higher in species where both
parents invest in caring for offspring. The offspring tends to have longer development
periods which may indicate that intensive parental care is necessary for their survival and
success.
2. The fossil record suggests that the major transitions in human evolution occurred in
Africa: The first hominins, the first members of the genus Homo, and the first members of
our subspecies (Homo sapiens sapiens) all are found there.
A. Please assign approximate dates to these three transitions.
The first major transition in human evolution occurred with the appearance of the
first hominins around 6-7 million years ago. The first members of the genus Homo appeared
approximately 2-2.5 million years ago, and the first members of our subspecies, Homo sapiens
sapiens, emerged around 300,000 years ago.
B. There were at least three major dispersals of hominins from Africa: some early members
of the genus Homo (probably H. ergaster) about 1.75 million years ago, H. heidelbergensis
roughly one million years later and, most recently, Homo sapiens sapiens about 70 thousand
years ago. Did the entire population of Homo sapiens sapiens leave Africa at that time? If
not, are there identifiable lineages that stayed in Africa?
The dispersal of hominins from Africa occurred at least three times. The first
dispersal was around 1.75 million years ago when some early members of the genus Homo,
probably H. Heidelbergensis left Africa. The second dispersal occurred roughly one million
