Life
The earliest fossilized form of life was living about 3.5 billion years ago. At this point all of life consisted of microorganisms and algae. Now for a fossil to even form is a rare occurrence. Conditions must be just right for a soft-tissue body to get through not decompsing or being eaten by other animals or some other natural occurrence that would destroy the skeletal system, if a skeleton is present. Only a microscopic portion of the organisms that die ever make it to the fossil stage. Only a small portion of the small portion of life forms that become fossils actually get discovered and studied.
The oldest fossil of a multi-cellular organism was found in Michigan and is reported to be 2.1 billion years old. About 600 million years ago aquatic worms appeared. About 400 million years ago the first vertebrates appeared. All of life at that time was in the water. Rhipidistians were primitive fish with muscular lobes for fins. These fish had the ability to shuffle on land. They came out of the water during droughts to move to another area where water was available. Basically, these were gill breathers with the ability to gulp air and then extract the needed oxygen. These fish were able to exist because they had adapted to the drying up of waterholes...they just crawled to the next water hole. As the droughts became more severe natural selection favored those fish that were able to survive out of water for longer periods of time. These fish became our first reptiles.
Finally about 200 million years ago, mammals evolved. We all basically not only share the same primate ancestors but can trace our family tree back to 150-200 million years ago to a shrew-like mammal. Well, we really can go back to the aquatic worms or even further to micro-organisms living in the water.
The Mesozoic time period was also known as the "Age of Reptiles." The first known mammals and birds split away from the dinosaurs. The dinosaurs had a two hundred million year reign. What happened 65 million years ago? The dinosaurs all died out. But there is proof that they existed and ceased existing 65 million years ago not six thousand years ago like some believe.
Jerry Seinfeld, in his hilarious 1993 book, SeinLanguage, talks about the possibility of finding out what happened to the dinosaurs and compared it to the Kennedy Assasination. He joked that we will never know about the dinosaurs because we cannot even figure out what happened 40 years ago. How can we possibly figure out what happened 65 million years ago?
The first bird, Archaepterx, is clearly a descendant from reptiles. Then came mammals. Tim M. Berra, who wrote Evolution and the Myth of Creation, states that primates, the mammalian order to which humans belong, arose and were widespead 38 million years ago.
Jackie Wellman
www.jackiewellman.com
