Geological Time Uncoiled
Many excellent books have been written about evolution, starting with Darwin’s two classics: On the Origin of Species and The Descent of Man. What Darwin learned from observation and fossil records, modern scientists can now amplify through their knowledge of DNA and new branches of science, such as molecular biology, biogeography, and radiometric dating.
To summarize the modern evolutionary overview from Why Evolution is True, Jerry A. Coyne wrote: “The first organisms, simple photosynthetic bacteria, appear in sediments about 3.5 billion years ago, only about a billion years after the planet was formed. These single cells were all that occupied the earth for the next 2 billion years, after which we see the first simple ‘eukaryotes’: organisms having true cells with nuclei and chromosomes. Then, around 600 million years ago, a whole gamut of relatively simple but multicelled organisms arise, including worms, jellyfish, and sponges. These groups diversify over the next several million years with terrestrial plants and tetrapods (four-legged animals), the earliest of which were lobe-finned fish appearing about 400 million years ago.
“Fifty million years later we find the first true amphibians, and after another 50 million years reptiles come along. The first mammals show up around 250 million years ago (arising, as predicted, from reptilian ancestors), and the first birds, also descended from reptiles, show up 50 million years later.
“Humans are newcomers on the scene—our lineage branches off from that of other primates only about 7 million years ago, the merest sliver of evolutionary time. Various imaginative analogies have been used to make this point, and it is worth making again. If the entire course of evolution were compressed into a single year, the earliest bacteria would appear at the end of March, but we wouldn’t see the first human ancestors until 6 a.m. on December 31. The golden age of Greece, about 500 BC, would occur just 30 seconds before midnight.” (Coyne, 2009)
This certainly puts human existence on this planet into perspective. In Darwin’s time, DNA was unknown, continental drift was unknown, radioisotope dating was unknown, and no fossils had been discovered of our proto-human ancestors. Despite those limitations, after a lifetime of study, Darwin concluded in The Descent of Man: “We thus learn that man is descended from a hairy quadruped, furnished with a tail and pointed ears, probably arboreal in its habits, and an inhabitant of the Old World.” (Darwin, The Descent of Man, 1871) Was Darwin correct? (to be continued in the next post)