I've made a rather arbitrary vow to read 25 plays and 200 poems before reading another novel. I will attempt to comment on those 25 plays and whatever poems I wish to.
There are three factors which may control our existence: fate, chance, and choice. You can rename these any way you like (fate may be Divine Providence, predestination, economic determinism, chance may be hazard or luck, choice may be action or will), but those are the options.
All, three, in some way, influence biology. We can easily call our genetic makeup fate or chance, and yet we have choice in what to do with it. But biology can complicate things.
In "King Lear," the bastard Edmund is focused on biology when he says "Why bastard? Wherefore base?/ When my dimensions are as well compact,/ My mind as generous, and my shape as true/ As honest madam's issue?" (I.ii.6-8). Later, he has a wonderful soliloquy about people who blame fate for the results of their own actions:
"This is the excellent foppery of the world, that when we are sick in fortune, often the surfeits of our own behavior, we make guilty of our disasters the sun, the moon, and stars; as if we were villains on necessity; fools by heavenly compulsion; knaves, thieves, and treachers by spherical predominance; drunkards, liars, and adulterers by an enforced obedience of planetary influence; and all that we are evil in, by a divine thrusting on. An admirable evasion of whoremaster man, to lay his goatish disposition on the charge of a star" (I.ii.135-146).
This is an excellent indictment of those who pass blame; Edmund seems to suggest that we make our own destinies, that our fortunes are "often the surfeits of our own behavior," that it is our actions which determine our lives, and we shouldn't blame the stars. However, he continues:
"My father compounded with my mother under the Dragon's Tail, and my nativity was under Ursa Major, so that it follows I am rough and lecherous. Fut! I should have been that I am, had the maidenliest star in the firmament twinkled on my bastardizing" (I.ii.146-152).
Interesting, here the emphasis seems to be on biology; Edmund says he would be what he is regardless of the stars. Is this not also fate? Is the suggestion that the individual is what he is regardless of any other factors, that Edmund was born a villain? Certainly Edmund doesn't blame the stars for his villainy.
However, this isn't necessarily fate; it is social convention/environment that helped to shape Edmund into a villain. He hates being an illegitimate child; he wants the benefits of being a legitimate child. He's also about a year younger than his brother. If Edmund hadn't been born into society where, by convention alone, Edgar gets all the benefits of family by a) being born legitimate and b) being born first, would Edmund have become a villain? Probably not. Edmund had no control over his own birth or social convention, however, so in a sense he is fated to his villainy; if born in different circumstances, he would not have been a villain. Still, he has some choice here; he can choose how to deal with his status as a bastard, and after all, his father does still treat him alright.
So biology and social convention is involved: all three factors of fate, chance, and choice go into Edmund's villainy. However, no divine control has anything to do with it.
This leads to my next question/point on King Lear. In this play, written in the early 17th century, some form of the word "nature" appears every other line. To what extent can we use 21st century understanding of genetics and biology in interpreting it. I think to a great extent. First, after four centuries of criticism, any new ways of approaching Shakespeare help keep the text meaningful. Secondly, as science becomes more and more important to our lives and philosophy, we can use literature to help us making meaning out of the science.