Issues or Controversies
Scientists said the discovery, reported in the current issue of the journal Nature, indicated that by 50 million years ago the primate family tree had split into its three main branches tarsiers, lemurs and the simians, or higher primates, that include apes and monkeys and eventually humans. Earlier evidence put the branching at 35 million to 40 million years ago. Some issues are:
- Primates are facing an impending extinction crisis, driven by extensive habitat loss, land use change and hunting.
- Daily and seasonal variations in temperature, annual cycles of precipitation, and larger swings in climate shape adaptations of plants and animals and ultimately may determine their survival. Changes in global and regional climates apparently had profound effects on the evolutionary history of primates.
- Primates are endangered it is due to the loss of their natural ecosystems.
- Geneticists have come up with a variety of ways of calculating the percentages, which give different impressions about how similar chimpanzees and humans are. The 1.2% chimp-human distinction, for example, involves a measurement of only substitutions in the base building blocks of those genes that chimpanzees and humans share.
- DNA have also been deleted, duplicated over and over, or inserted from one part of the genome into another. When these differences are counted, there is an additional 4 to 5% distinction between the human and chimpanzee genomes.
The strong similarities between humans and the African great apes led Charles Darwin in 1871, to predict that Africa was the likely place where the human lineage branched off from other animals that is, the place where the common ancestor of chimpanzees, humans, and gorillas once lived. The African great apes, including humans, have a closer kinship bond with one another than the African apes have with orangutans or other primates. Hardly ever has a scientific prediction so bold, so 'out there' for its time, been upheld as the one made in 1871, that human evolution began in Africa.
