(Please see here for previous posts in this series.)
One of interesting things about evolution is that it seems to be speeding up with time. Earth was formed about 4.7 billion years ago and it took about a billion years for the first single-celled life to appear about 3.5 billion years ago. It then took another 2.5 billion years for the first multi-cellular life form (like sponges) to appear. So everything else, all the insects, animals, and birds, came into being within the last one billion years or so.
One reason that things seem to be speeding up is that once complex organisms appeared, selection advantages increased due to more sophisticated competition among them. For example, when you have a predator-prey relationship, the prey species will have a huge selection advantage for those qualities that enable it to elude the predator (such as the ability to run faster or climb quicker or hide better or hear and smell better) while the predator will also have a huge selection advantage for those features that make it better able to capture prey (run faster, jump higher, and more acute vision, hearing and smell.) It is like an arms race. Two nations that are locked in a battle for supremacy are more likely to rapidly develop sophisticated weaponry than a nation without enemies.
Such factors, along with things like sexual selection, speed up the evolutionary process considerably, by increasing the selection advantage.
But new discoveries keep coming in and just this year, researchers have found that bacteria and viruses are also speeding up the process of evolution. Scientists at Rice University report that “the speed of evolution has increased over time because bacteria and viruses constantly exchange transposable chunks of DNA between species, thus making it possible for life forms to evolve faster than they would if they relied only on sexual selection or random genetic mutations.” Theories like this support suggestions that there is a selection advantage for those organisms that are more adaptable to change. In other words, evolution favors those organisms that evolve more readily, leading to ever-increasing rates of change.
In fact, the problem with the evolution of species is not (as some religious people would have you believe) whether it occurs at all but that it is impossible to stop it from occurring. Almost invariably, when some members of a species get isolated from the rest for whatever reason, they begin to diverge. This is why the isolation of islands makes them excellent breeding grounds for new species. All the islands smaller than New Guinea account for one-thirtieth of land surface but contain about one-sixth of the total number of known species (Almost Like a Whale, Steve Jones, p. 345). In the Caribbean, for example, different lizards have different kinds of legs suitable for the kinds of vegetation that they climb on. In 1977, when lizards from one island were moved to another that had no lizards and only plants with thin twigs, within ten years their legs had evolved to meet the needs of the new vegetation by becoming stubby (Jones, p. 96).
But Darwin also proposed that one did not need actual physical separation like islands for speciation to occur. Diversity could arise within the same geographical area as organisms adapted to fit different niches in the same environment. Just yesterday it was reported that new evidence suggests that the two species homo habilis and homo erectus lived side by side at the same time, challenging the earlier idea that there was a linear progression from homo habilis to homo erectus to us, homo sapiens. The news report of the findings says that “The fact that the two hominid species lived together in the same lake basin for so long and remained separate species, Meave Leakey said in a statement from Nairobi, “suggests that they had their own ecological niche, thus avoiding direct competition.” “
Zoos face this problem with trying to preserve rare species. Although the zoos are trying to preserve the animals that are being lost in the wild, the very fact that zoo animals breed within a small group paradoxically causes them to actually accelerate their evolution into new forms. (Jones, p. 47)
As a result of all these factors favoring evolution, “Over the past five hundred million years, through all its ecological alarms and excursions, new kinds appeared at an almost constant rate. A survey of tens of thousands of marine animals over that time gives a rate of four hundred and fifty new species a year.” (Jones, p. 231)
This is the last post in this series on evolution. To be frank, I had not expected it to be this long when I started but the breadth and scope of the subject just kept drawing me in deeper. While I will definitely return to this topic many times (because it is inexhaustible and new and interesting discoveries keep popping up), the planned and sequential nature of these posts will cease. My goal was to move the discussion of the theory of evolution away from a high level of generality and show that evolution is not just a good idea but that, like quantum mechanics and relativity, it is a theory that has been developed in great detail and its ramifications explored using a wide array of scientific tools.
The mathematics of evolution has played an important role in substantiating its claims and advancing our understanding of how it works. Charles Darwin would have found this highly amusing because he had great difficulty with mathematics as a student, struggling with even elementary algebra. Because of the complexity of biological systems, the probabilistic nature of the processes, and the interplay of organisms with other organisms and the environment in general, modern biological calculations use advanced mathematics, computer simulations, and game theoretical techniques in addition to the more conventional differential equations. There is even a new game by the creators of the Sims series that enables you to manipulate the conditions of evolution and see what happens. You can “determine the evolution of a species, from an amoeba to an inter-stellar race.”
This is how science works and how we build up knowledge. People with different skills and expertise bring them to bear on complex problems, publish so that it can be checked by others, and over time we create reliable knowledge. This does not mean that scientific knowledge is infallible by any means. It is not uncommon for people to find that new data or a different set of assumptions lead to quite different results, and so scientists continually probe for weaknesses.
But such revisions and critiques are of a very different class from those of people who reject scientific ideas as absurd simply because it conflicts with their intuitions or because they seem unimaginable, without looking into the details. Such people are doing the same thing as those who reject quantum mechanics and special relativity because the results seem so weird to them.
POST SCRIPT: Pampered elites
Jason Jones of The Daily Show has a very funny piece on how the very rich in this country don’t want to allow even the slightest thing to disturb their lives. People like the Kennedys, who vociferously support environmental causes everywhere else, turn against eco-friendly projects when those might have an infinitesimal impact on their own neighborhoods.