Actually, I don't think anyone in the know ever thought Jean-Baptiste Lamarck was stupid. I used to make fun of him, but no one has ever thought I am particularly in the know when it came to biology and theories of evolution.
Lamarck argued that giraffes might have evolved long necks by trying to reach up to eat leaves from tall trees. Lamarck's suggestion was that a mommy giraffe might have a baby giraffe with a longer neck because it had tried so hard to eat leaves from tall trees. Of course Darwin himself had no mechanism to explain his proposed evolutionary changes either. It was years later when the notion of mutation was introduced to explain fundamental genetic changes (neo-Darwinism).
[And let me also make it clear that this post relates to micro-evolution rather than macro-evolution. Evangelicals don't have problems with the idea, for example, that all the different varieties of dog might have come from a proto-dog. The question is how far back such processes can go--to a proto-cat-dog? a proto-mammal? And of course the question of human ancestry stands as the most divisive and potentially troubling question theologically.]
But genetics currently has apparently tweaked its understanding here--a fascinating instance to me of how theories that seem to be eliminated on one level can then come back in a different form on the next level of sophistication. [insert tribute to Thomas Kuhn]
Apparently there are genes that can "methylate" (a term I learned from Burt Webb) in more than one way, even over the course of our lives. What this means is that some characteristics of who we are can change because of our behavior. Motion can bring emotion. If we act loving toward others, we may very well get the feelings of love toward that person (I'm mixing a bunch of stuff together here, I suspect). I can be a person who does not typically do certain things but, over time, change into a person who does them. I'm sure I'm not quite explaining this quite right or as clearly as possible.
Behavior is not simply a matter of one gene, in the same way that a memory is probably not stored in a particular neuron. Nevertheless, however behavioral traits relate to core genetics, our environment can modify our predispositions by causing our genetic potential to "methylate" in various ways. In the case of male sperm, the way a male's genes are methylated at the time that sperm is created, will point our children in particular genetic directions and toward certain potential tendencies I have.
(Females, on the other hand, have all their eggs from before the time of their birth, so their specific behavior at the time of conception is irrelevant, leading Drury to some interesting thoughts on virgin births).
So women's eggs have certain behavioral predispositions from the genetic situation of their father and mother at the time of her conception, and men's sperm have certain behavioral predispositions from that male at the point when that sperm originated. In short, more than genetic potential is inherited. And because any mutation will proceed from what is methylated at the time of conception, male behavioral tendencies at the time sperm is created can, in fact, affect the behavioral tendencies our children inherit.
So Lamarck was not so stupid as I thought :-)
This sets my uninformed mind down many a strange trajectory. For example, most people seem to have a clear direction of sexual expression from their earliest sexual memories. The majority of individuals, without ever thinking about it, are attracted to the opposite sex. A minority of individuals, by contrast, are attracted to the same sex, also without ever having thought about it.
But are there individuals who are, for whatever reason, are in a middle zone where a particular set of circumstances might lead them in one or the other direction? If methylation can work this way (and I really have no idea what I am talking about), it would explain individuals like Anne Heche, who seem to go through phases of both orientations. It would also imply that there is a certain minority with bisexual potential who, by whatever experiences, might go one or the other direction... and/or back.
These are uninformed musings, following out certain lines of thought. I am not arguing for anything. But imagine how much there is that most of us do not know... and how confidently we must spout ignorance all the time.