Evolution
Mammals, including humans, evolved from reptiles. The transition from reptiles to mammals is extraordinarily well documented with the gradual transition of reptilian jaw bones to the three inner ear bones in man. At first glance such an idea seems quite preposterous. However, reptiles did sense sound through their jaws and the gradual steps of evolutionary development made sense at every point in the transition. The recent (2001) discovery of the Hadrocodium wui, a mammal like creature the size of a paper clip, adds to the intermediate steps demonstrated in this process.(3)
Man's closest living relative is the chimpanzee with which we share about 98 percent of our genetic information. We had a common ancestor with the chimpanzee between 5 and 8 million years ago. The African continent was a lush tropical forest at that time with many species related to modern apes and humans. We have many fossils of hominids that were either direct ancestors or near relatives of those that were ancestors.(4) They elegantly illustrate the increasingly human qualities with the changes in brain size and upright walking stance. In more recent times Africa become much drier and the forests gave way to a savanna that required upright walking rather than the grasping big toes that were an appropriate adaptation for dwelling in trees.
We know that evolution works through a now well understood structure of DNA in a double helix configuration. We have been able to read these sequences and compare them between individuals and between species. We have isolated many particular genes as the ones that are responsible for specifying particular functions and their failure has been linked to specific genetic diseases. The genes in an organism are a recipe for encoding proteins that are used to create all tissues and structures in the body.
The theory of common descent is supported by the substantial similarity in the genes of organisms that are closely related. Not only are 98 percent of human genes the same as chimpanzee genes, in many cases they share the same flaws. The nonfunctional gene to make vitamin C has been isolated in humans and related ape species. The differences are exactly as would be predicted given the time since each pair of species had a common ancestor. The location of these genes are in precisely the same DNA double helix location in each species.
Retroviruses are a class of virus that inserts its own DNA into the host's genes. Occasionally, these retroviruses leave evidence of an infection in the egg or sperm cells that are passed on to following generations. When organisms have the same genetic sequence from the same ancient infection in exactly the same location this is an additional proof that genes have been shared through an identical common ancestor.(5)
There have been over 100 cases of humans born with tails. In some cases this anomaly has been passed on to additional children. Several human tails have been found with up to five well-developed, articulating vertebrae. True human tails can be moved with voluntary muscles as with monkey species.(6)(7) This should not be surprising to any student of the human embryo. It is often said that ontogeny recapitulates phylogeny. This means that the growth of the embryo (ontogeny) expresses the sequence of evolutionary organisms from which we have evolved (phyogeny). At four weeks the human embryo will have four gill slits pouches and a tail. These features will appear in the embryos of all vertebrate species and reflect the evolutionary history of vertebrate species.(8)
These examples are only a tiny sampling of the evidence for common descent of all living organisms, including humans. The basic unit of energy storage, the adenosine triphosphate molecule (ATP), is the same in all species that have been studied. In all but very simple bacteria, the same ten step process is used to create usable biological energy from ATP and those steps are executed in exactly the same sequence. This is one of a great many commonalties that humans have with any common flower.
What does this mean for religion? The human brain has evolved as the other organs have evolved, like the heart, the kidney, or the skin. The functions of the brain well explain all of human consciousness. The theory of evolution is consistent with the human brain being a purely physical organ. When the brain dies, all of the physical functions that produce consciousness cease. A physical understanding of consciousness would imply that there is no consciousness or personal life after death. This prediction, that logically derives from evolution, is one of the underlying reasons behind the hysterical attacks on evolution from fundamentalists.
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