Genome: Chromosome 2 - Species

Until 1955, humans were thought to have consisted of 24 pairs of chromosomes until Albert Levan’s experiment. Levan concluded that humans have 23 pairs of chromosomes after counting the chromosomes in photograph books with captions stating that there were 23 pairs. While chimpanzees, gorillas, and orangutans have 24 pairs, humans are similar to apes. We humans are apes, yet we have one obvious difference: humans have one less chromosomes because a pair of ape chromosomes had fused together into us humans. Natural selection is where life forms are changing to suit our exposed physical environment. Humans are able to colonize different habitats whether it is hot, cold, high, low, marine, or desert environments. We are also the most abundant large animals living on the plant, about 6 billion of us add to about 300 million tons of biomass. Ridley ends the chapter by saying that human beings and chimpanzees are similar except for their genetic differences because genes are not sufficient, at least not in apes. Genes are recipes for anatomy and behavior, as well as natural selection.