The line in this game represents complexity, with 1 being the least complex and 100 the most.
Where do you expect the marker to be after 5 or 50 or 500 coin tosses? Probably not at square one.
Suppose the game begins with the marker placed at the left-most point on the line. If the coin lands tails when the marker is at the extreme left, you simply toss again. These are the rules of change unless the marker happens to be at the left-most or the right-most points. If the coin lands heads, you move the marker one space to the right if the coin lands tails, you move the marker one space to the left. A marker on a line changes position as a result of a coin toss. This is analogous to the random walk depicted in Fig. Complexity increases from life's beginning because of the initial conditions, not the laws. Parasites evolve from free-living ancestors, and the effect is often a move toward greater simplicity, with parasites losing organs and abilities possessed by their ancestors (ref. However, that is not because the “laws of motion” of natural selection inherently favor complexity. Of course, if life starts simple, evolution by natural selection will lead the average complexity of the biota to increase. This is the vital contrast that separates Darwin from Lamarck, who saw evolution as leading lineages to move through a preprogrammed sequence of steps, from simple to complex. Everything depends on which traits do a better job of allowing organisms to survive and reproduce in their environments. There is no inherent tendency for life to grow bigger or faster or harder or slimier or smarter. For these reasons, Darwin's theory is better described as “the origin of diversity by means of natural selection.”Īnother important feature of Darwin's concept is that the direction in which selection causes populations to evolve depends on accidents of the environment. True, the process he describes produces species, but it produces traits and taxa at all levels of organization.
Even so, “species” is not the central concept in Darwin's theory. This is the lesson we learn from other vague concepts – from rich and poor, hairy and bald, tall and short a vague boundary does not entail that no one is rich, or hairy, or tall. This vague boundary between variety and species is no reason to deny the existence of individual species, nor did Darwin do so ( 2, 36). It is convenience, not fact, that leads us to classify different degrees of divergence in different ways (ref. When 2 populations split from a common ancestor and diverge from each other under the influence of different selection pressures, they begin as 2 populations from the same variety, then they become 2 varieties of the same species, and finally they reach the point where they count as different species. I say this because Darwin had doubts about the species category he regarded the difference between species and varieties as arbitrary. 1) says that the origin of species is the “mystery of mysteries” that he proposes to solve, his solution of the problem is in some ways a dissolution. To characterize Darwin's theory, what could be more natural than to cite the title that Darwin gave to his own book ( 1)? How could this formulation lead us astray? In fact, there is trouble here, and it is of Darwin's own making.