What's Next in Human Evolution?

A friend recently asked me, “What’s the next step in human evolution?” As much as I have read on the topic of evolutionary biology and psychology, I had never really considered this. I think there are few reasons for this.

These reasons are outlined below:

1. Evolution does not imply progress.
There is so much misunderstanding about what evolution means. The first thing to remember is that evolution does not lead to better organisms. The engine behind evolution, or change, is natural selection. Dictionary.com defines natural selection as, “The process in nature by which, according to Darwin’s theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated.” That brings us to rule 2.

2. Evolution is simply an organism’s adaptation to a local environment.
Paleontologist Stephen Jay Gould had great way of describing rule 2:

    “You can be the best fish in the pond but, if the pond dries up, you’re dead. You can rule the earth for over one hundred million years and be perfectly adapted to your environment (as in the case of the dinosaurs) but if a large enough meteorite hits the earth, you’re extinct.”

Biologists continue to be amazed by the dramatic diversity of species that have been generated over millions (and sometimes billions) of years. Many species so well adapted to their local environments that their existence is a necessity for the entire local ecosystem (see Interesting Thing of the Day). This is why scientists study ecological niches to discover major climate changes – because these ecosystems are so sensitive to minor fluctuations in global climate.

3. Evolution often takes major, dramatic leaps in a short period of time.
The quote above from Gould about dinosaurs points out how quickly a major jump, or what he called, “punctuated equilibria,” can occur. These major changes can happen on a very localized level or it can impact an entire planet – as in the example of dinosaurs. In fact, we have every reason to believe that humans would never have come into being without the mass extinctions that occurred. Contrary to popular belief, humans did not co-exist with dinosaurs. The very first mammals emerged around this same time and were small and fast enough to stay out of the jaws of hungry dinosaurs. After the mass extinction, mammals owned the planet. However, with no meteorite (or some scientists speculate comet) dinosaurs would have continued trucking along. They had ruled the Earth for 100 millions years and there is no reason to believe that would have been challenged.

4. The force behind evolution is genetic mutation.
Though there is currently debate about the role of proteins in the transmission of heredity (see The next revolution in science?) the central dogma in molecular biology is that random genetic mutation is the only way an organism can change. If a mutation helps an organism adapt to their local condition (rule 2) then it is said to have a high “fitness factor”. Translation: if this particular organism has a slight advantage over other organisms because of this mutation, they will be more successful at mating, and having stronger offspring (with a higher fitness factor). The genetic mutation could also be horrific – as many genetic diseases are – and this can cause an organism to die young or have a low fitness factor. Eventually, these mutations are weeded out in the population.

Also based on rule 2, a genetic mutation with a high fitness factor in one local environment could have a low factor in a new environment. The classic case is sickle cell anemia. Sickle cell is a genetic disease, much more common in people from Sub-Saharan Africa, which alters the shape of red blood cells. This makes it very difficult for their blood cells to bind to oxygen. However, this same mutation also makes it very difficult to contract malaria. So, when people from these areas of Africa began moving into other climates where malaria was not a problem, their mutation was not longer an asset, it was a liability.

Conclusion & Summary
To summarize, evolution has no purpose or direction. It is simply random mutations occurring in an organism’s DNA that make it either more or less adapted to the circumstances in which they find themselves.

Humans are probably the lest well adapted creatures to the planet. Instead we have managed to use tools to shape the environment to us. Natural selection is now being executed by humans rather than nature on a scale never before seen. This appears to be unique among life on Earth. With the advances of science and medicine even some of the worst genetic disorders (or mutations) are going to be treatable and this will only get better with time. So, rather than continuing to evolve at a rapid clip, I believe humans are slowing down because of technology. I believe we have plenty of ability to continue transforming the planet and solar system to our needs for thousands of years to come without much change in our morphology or DNA. Gould’s anecdote about the dinosaurs is a grim reminder of a potentially fatal future however. Punctuated equilibria, whether in the form of a comet or several nuclear bombs, is real and it has shown up more than once in our planet’s history. I hope for a more optimist future where humans reach out for the stars and colonize other worlds – perhaps in new galaxies millions of years from now. As for the future of humanity, once our local environment changes significantly and we master the genetic code, the possibilities are limitless.

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