Once again for Perry ..
Noting the size of the cranium and therefore the size of the skeleton of which these skulls were attached to.
An important factor to consider in biological evolution is the new scientific understanding of DNA.
DNA
Through news accounts and crime stories, we’re all familiar with the fact that the DNA in our cells reflects each individual’s unique identity and how closely related we are to one another. The same is true for the relationships among organisms. DNA, or deoxyribonucleic acid, is the molecule that makes up an organism’s genome in the nucleus of every cell. It consists of genes, which are the molecular codes for proteins – the building blocks of our tissues and their functions. It also consists of the molecular codes that regulate the output of genes – that is, the timing and degree of protein-making. DNA shapes how an organism grows up and the physiology of its blood, bone, and brains.
DNA is thus especially important in the study of evolution. The amount of difference in DNA is a test of the difference between one species and another – and thus how closely or distantly related they are.
While the genetic difference between individual humans today is minuscule – about 0.1%, on average – study of the same aspects of the chimpanzee genome indicates a difference of about 1.2%. The bonobo (Pan paniscus), which is the close cousin of chimpanzees (Pan troglodytes), differs from humans to the same degree. The DNA difference with gorillas, another of the African apes, is about 1.6%. Most importantly, chimpanzees, bonobos, and humans all show this same amount of difference from gorillas. A difference of 3.1% distinguishes us and the African apes from the Asian great ape, the orangutan. How do the monkeys stack up? All of the great apes and humans differ from rhesus monkeys, for example, by about 7% in their DNA.
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. A comparison of the entire genome, however, indicates that segments of 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.
No matter how the calculation is done, the big point still holds: humans, chimpanzees, and bonobos are more closely related to one another than either is to gorillas or any other primate. From the perspective of this powerful test of biological kinship, humans are not only related to the great apes – we are one. The DNA evidence leaves us with one of the greatest surprises in biology: the wall between human, on the one hand, and ape or animal, on the other, has been breached. The human evolutionary tree is embedded within the great apes.
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 DNA evidence shows an amazing confirmation of this daring prediction. 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.
The DNA evidence informs this conclusion, and the fossils do, too. Even though Europe and Asia were scoured for early human fossils long before Africa was even thought of, ongoing fossil discoveries confirm that the first 4 million years or so of human evolutionary history took place exclusively on the African continent. It is there that the search continues for fossils at or near the branching point of the chimpanzee and human lineages from our last common ancestor.
