We know that our ancestors were hunters and thrived on red meat, which gave them a greater risk towards different diseases. Questions are brought up wondering why this lifestyle did not kill them, and what possibly gave them immunity from the pathogens in the many animals they ate regularly.
It is seen in the relationship between ape and human DNA that up until 3 million years ago, they shared the same sugar, but then a slightly different sugar was substituted in humans. The researchers at the University of California , San Diego say that this change in sugar was a result in a mutation of a gene found in humans. This mutation happened in between the time span of walking upright and brain size expansion, around the time that homo erectus emerged.
This switch in sugar was further stimulated because around the time of the switch, our ancestors became more hunter-like, eating more red meat, which contains great amounts of Neu5Gc. This is the sugar found in cells of apes, but not humans. These researchers believe that the immune system responded and saw this sugar as something that needed to be destroyed. The change in sugar at the time had a major impact on human evolution.