Evolution is one of those topics that confuses and sometimes frustrates people. In my experience, the confusion comes by mixing concepts from two different theories on evolution.
I want to clarify the meaning of the term, "theory." A scientific theory is not “a random guess.” Picking the winning combination of numbers in the lottery is a random guess. Although sometimes guessing does take place when doing science, a theory is not one of those times. A scientific theory is an attempt to explain why a complex system works the way it does. A theory is like thoughtfully assembling the pieces of a jig-saw puzzle and then seeing a complete and meaningful picture. A theory sees how related phenomena are connected, and how, together, they interact and result in something larger. Much larger.
For example, Cell theory explains how the cooperative arrangement and operation of tiny cells collectively result in a whole living individual. That is how and why living things work – because of the collective operations that go on inside their many, many cells. This is not a wild guess. It is a testable explanation that is substantially consistent with objective observations.
There are two theories of evolution that people often blend together as if they are a single theory.
First, there is Lamarck’s theory of evolution. Jean-Baptiste Lamarck was an early 19th century naturalist who preceded Charles Darwin. According to Lamarck, living things evolved out of necessity. That is, evolution was “pushed” by individuals in real time. If a short-necked giraffe saw a tree with tasty leaves, that individual giraffe simply made its neck longer and fed on those otherwise unreachable leaves. Yay, giraffe!
Inspiring and hopeful. Except the evidence doesn’t support this theory.
Lamarckian evolution theory gave us the following favorite evolution expressions – that are completely wrong:
- Only the strong survive. As if it is possible to predict which individuals of a population will survive to adulthood based on our perception of desirable traits. Since environmental conditions are not predictable, it is not possible to know with certainty which mix of traits is best. We can only do that after-the-fact.
- Living things need to adapt to their environment. This expression propagates the unsupported viewpoint that all living individuals are consciously engaged in an ongoing assessment of their physical attributes in terms of their dynamic surrounding environment. And then, if their perceived need arises, they initiate internal actions to reconfigure themselves to achieve the best outcome for themselves. This goes for bacteria, animals and the sycamore tree down the street. Although humans DO have the cognitive ability to abstractly model their lives and make assessments of their “needs,” they still have no way to reconfigure their physical presence in response – in a way that can be genetically passed to their future offspring.
- The complex battle of life. A Lamarckian metaphor – not evident in a less dramatic Darwinian viewpoint.
There are many more. But I think I’ve made my point.
Second, is the theory of evolution proposed simultaneously in the late 1800s by Charles Darwin and Alfred Russel Wallace. This theory was not accompanied by the kind of cognitive narrative we see with Lamarck. It was more passive.
According to Darwin's and Wallace's theory, evolution is a RESULT.
Darwin (and others before him) observed that there is variety among individuals of any given population of living things. That few individuals of a generation survive to sexual maturity. Environmental stresses act unequally on the differing individuals in the population, many of them unable to continue operations (dying). Although Darwin and Wallace knew nothing about genetics, they did understand the principle of reproduction with inheritance. Those who survived to adulthood passed copies of their traits (their genes) to offspring. And given their inheritance, offspring resembled their parents.
That is genetics and ecology. Darwinian evolution is simply genetics and ecology (environment).
Evolution is the result of disruptions in the flow of genes from one generation to the next. In other words, the environment shapes the flow of genes from one generation to the next.
Evolution is nothing more complex than a statistical outcome in population genetics. There is no evolutionary direction. There are only historical traces left behind. Evolution is not a plan. It is an unplanned result.
It is disheartening to think this way, but life on Earth is mostly about death. It is a numbers game where inheritance and chance have a big influence.
So, when discussing evolution try to keep this in mind. And do what you can to avoid bringing Lamarck’s purposeful thinking into discussions about Darwinian evolution. Remember, it’s just genetics and ecology.