Well, all that algebra was lots of fun,12 but what good did it do us? Not an enormous amount, except that it shows us (not surprisingly), that allele frequencies are likely to change as a result of viability selection, and it gives us a nice little formula we could plug into a computer to figure out exactly how. One of the reasons that it's useful13 to go through all of that algebra is that it's possible to make predictions about the consequences of natural selection simply by knowing the pattern of viaiblity differences. What do I mean by pattern? Funny you should ask (Table 1).
Before exploring the consequences of these different patterns of
natural selection, I need to introduce you to a very important result:
Fisher's Fundamental Theorem of Natural Selection. We'll go through
the details later when we get to quantitative genetics. For now all
you need to know is that viability selection causes the mean fitness
of the progeny generation to be greater than or equal to the mean
fitness of the parental generation, with equality only at equilibrium,