| Date | November 2015 | Marks available | 1 | Reference code | 15N.3.SL.TZ0.10 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 10 | Adapted from | N/A |
Question
Modern human mothers give birth to proportionately larger infants than apes do, but it is not clear when this change occurred over the course of human evolution. The graph shows the infant mass relative to mother mass in primates, extinct hominids and modern humans.
State the infant mass relative to mother mass of Homo sapiens.
Outline the difference in infant mass relative to mother mass in extinct hominids and modern humans.
Suggest a hypothesis, based on evidence in the data, for when the shift to giving birth to larger infants occurred in the evolution of humans.
Suggest one disadvantage of infants being born with a relatively large size in humans.
Markscheme
5.8(%)
Accept answers in the range of 5.7(%) and 5.9(%).
slightly less/similar (infant mass relative to mother mass) in extinct hominids than modern humans / vice versa
a. shift (to birthing larger infants) occurred with Australopithecus afarensis/after Ardipithicus ramidus;
b. infant mass relative to mother mass ratio lower in Ardipithecus ramidus than Australopithecus afarensis;
c. evidence limited since time lines not indicated/may be overlap;
a. obstetric problems / difficulty giving birth / prenatal problems;
b. carrying/transporting a large infant could be difficult;
c. larger infants require more food;
Examiners report
Most candidates scored well in their interpretation of the data.
Most candidates scored well in their interpretation of the data.
Most candidates scored well in their interpretation of the data.
Most candidates scored well in their interpretation of the data.
