Acceptance of Darwin’s brilliant deduction on evolution as the source of all biological diversity was brought to the world in 1859 with the publication of “The Origin of Species.” Now, almost 160 later, not all are convinced. The problem of accepting, really a matter of understanding, evolution becomes the sharpest when considering human origins.
All religions have their own take on the origin of mankind, and there are thousands of different stories. Abrahamic religions dominate with over half the world’s population and share the story of Adam and Eve. That said, much of modern religious thought sees no intrinsic conflict with evolution, but fundamentalist wings of many religions persist in denying what is obvious to science.
The United States is arguably the most scientific nation in the world based on the number of peer-reviewed scientific publications. Simultaneously, it is one of the more backward nations of the developed world with 4 in 10 adults believing that God created man in his image, with no evolutionary if, ands, or buts.
Besides the religious conflict about human origins is the problem of diversity itself. Who would ever have guessed that a whale is just a proto-cow that wandered back into the sea and decided to stay? Or that today’s chickens are yesterday’s dinosaurs. Many incrementally small changes over long periods of time have created the diversity we see today. We obviously can’t run experiments over billions of years to prove the concept once and for all, but experiments which prove evolution can be done in real time over the course of just a few years.
Johnathan Losos in his book “Improbable Destinies” described two such studies, one with guppies and one with lizards that clearly demonstrate how mutations and natural selection impact diversity.
The guppy study involved different populations of guppies in streams in Trinidad. It was observed that guppies in pools above waterfalls were much more flamboyant with colorful spots compared to guppies living in pools below waterfalls where drabness prevailed. The hypothesis was that the colorful guppies enjoyed an essentially predator free environment. Those below the falls were in pools which contained predators and therefore only the bland survive.
A simple but elegant experiment over the course of four years showed that transferring colorful guppies to a downstream pool free of other guppies but with predators causes the descendants to become much less gaudy and therefore less likely to be preyed upon. Random mutations among the guppies that produced less visible descendants were less likely to attract attention of predators.
The lizard study, actually brown anoles, also employed moving a population from one isolated locale to another. In this study the anoles from one small island were transferred to other small islands some with and some without predators. In a few short seasons, the anoles’ descendants on the islands with predators had shorter legs that allowed more facile movement into the upper branches of shrubs. Predation was the selective pressure, mutations allowed for the variance in leg length.
Real evolutionary morphological changes can be observed in a short time period, so now just imagine what kinds of changes can occur given millions and billions of years with different mutations and different selective pressures.
Charles Darwin (and Alfred Wallace who independently came to the same conclusion as Darwin) were right. We humans are evolutionarily related to every other living thing on the planet.