Answers to Exploration Questions: Human evolution

Answer: As hominins evolved, their bodies became larger, their skulls became larger, and their bone structure became better adapted for walking upright. For example, their big toes became smaller and pointed forward — more for propulsion (upright walking) rather than climbing. Also, their faces became flatter and their brow ridges smaller.

Answer: Paleontologists studying an ancient primate would be interested in other fossils discovered at the same site in order to recreate and understand the primate’s environment. On Rusinga Island, paleontologists learned that the ancient primate Proconsul lived in two distinct environments: a watering hole in a dry region, and a forest. This discovery revealed that Proconsul, like modern humans, were able to adapt to different environmental conditions.

Answer: Most of our DNA is in 23 sets of chromosomes in the nucleus, but there is some in the mitochondria, the cell’s energy generators. Half of the DNA in the nucleus comes from your mother and half from your father. Y-chromosomes are half of one set of the 23 sets of nuclear DNA chromosomes. Since only males have a Y chromosome, Y-chromosome DNA passes from father to son. Mitochondrial DNA passes only from a mother to her children. Scientists who study evolution are interested in Y-chromosome DNA and mitochondrial DNA because they come from only one parent — they don’t get “shuffled” like DNA in the nucleus. Scientists can use them to look millions of years into the past to reconstruct events in human evolution and human migrations.