The genotype (the total of all genes in a body) is like the complete set of 46 binders. Each of the binders is a chromosome. Human body has 23 pairs= 46 chromosomes. (Other animals have a different number of chromosomes.) Each page in the binder is a gene. Phenotype is the list of all observable behavior exhibited by an organism.
The programmer's actual role is rather more like that of a father teaching his son to play chess. He tells the computer the basic moves of the game, not separately for every possible starting position, but in terms of more economically expressed rules. He does not literally say in plain English 'bishops move in a diagonal, but he does say something mathematical equivalent... Then he might program in some 'advice' written in the same sorry of mathematical or logical language, but amounting in human terms to hints such as 'don't leave your kind unguarded' or useful tricks such as 'forking' with the knight... The important point is this: when it is playing, the computer is on its own and can expect no help from its Master.
In terms of how many babies to have or eggs to lay.. The gene that decides is not the one which is preprogrammed with a number but it is one that is preprogrammed to estimate the right number in real time.
Will it always pay a mother to treat all her children equally, or might she have favorites? Should the family function as a single cooperating whole, or are we to expect selfishness and deception even within the family? Will all members of a family be working towards the same optimum, or will they disagree about what the optimum is? These are the questions we try to answer in the next chapter.
Even if parents do not want to show favoritism, could it be that children grab favored treatment for themselves? More strictly, would genes for selfish grabbing among children become more numerous in the gene pool than rival genes for accepting no more than one's fair share? This matter has been brilliantly analyzed by Trivers in a paper of 1974 called "parent offspring conflict"
Sometimes, as we have seen, one member of a litter is a runt [an animal that is smaller than average]. He is unable to fight for himself as strongly as the rest, and runts often die. We have considered the conditions under which it would actually pay a mother to let a runt die... A gene that gives the instruction "Body, if you are very much smaller than your litter mates, give up the struggle and die" could be successful in the gene pool, because it has a 50% chance of being in the body of each brother and sister saved, and its chances of surviving in the body of the runt are very small anyway.
But the following is a reasonable strategy for a parent who is undecided as to what is her optimum clutch [batch] size for the current year. She might lay one more egg than she actually 'thinks' is likely to be the true optimum. Then, if the year's food crop should turn out to be a better one than expected, she will rear the extra child. If not, she can cut her losses. By being careful always to feed the young in the same order, say in order of size, she sees to it that one, perhaps a runt, quickly dies, and not much is wasted on him, beyond the initial investment of egg yolk or equivalent. From the mother's point of view, this may be the explanation of the runt phenomenon. He represents the hedging if the mother's bets. This has been observed in many birds.
A child will lose no opportunity of cheating. It will pretend to be hungrier than it is, perhaps younger than it is, more in danger than it really is. It is too small and weak to bully its parents physically, but it uses every psychological weapon at its disposal: lying, cheating, deceiving, exploiting right up to the point where it starts to penalize its relatives more than its genetic relatedness to them should allow. Parents, on the other hand, must be alert to cheating and deceiving, and must try not to be deceived by it. If the parent knows that its child is likely to lie about how hungry it is, it might employ the tactic of feeding it a fixed amount and no more, even though the child goes on screaming. A. Zahavi has suggested a particularly diabolical form of child blackmail: the child screams in such a way as to attract predators deliberately to the nest. The only way a parent can stop it screaming is to feed it.
But they [parasitic brood] do not lack ruthlessness. For instance, there are honeyguides who, like cuckoos, lay their eggs in the nest of other species. The baby honeyguide is equipped with a sharp hooked beak. As soon as he hatches out, while he is still blind, naked and otherwise helpless, he scythes and slashes his foster brothers and sisters to death: so they don't compete for food. The familiar British cuckoo achieves the same result in a slightly different way. It has a short incubation time and so the baby cuckoo manages to hatch out before its foster brothers and sisters. As soon as it hatches, blindly and mechanically, but with devastating effectiveness, it throws the other eggs out of the nest. And therefore the attention of the foster parents entirely to itself.
“An animal's behaviour tends to maximize the survival of the genes "for" that behaviour, whether or not those genes happen to be in the body of the particular animal performing it.[2]
Bruce effect: Male mice [presumably not the father of the unborn baby] secrete a chemical which when smelt by a pregnant female can cause her to abort.
It is a rather horrible but very subtle argument. A parent may be expected to desert the moment it is possible for him or her to say the following: "This child is now fat enough developed that either of us could finish off rearing it on our own. Therefore it would pay me to desert now, provided i could be sure my partner would not desert as well. If i did desert now, my partner would do whatever is best for her/his genes. He/she would be forced into making a more drastic decision than i am making now, because i would have already left. My partner would "know" that if he/she left as well, the child would surely die. Therefore assuming my partner will take the decision that is best for his/her own selfish genes, i conclude that my best of course of action is to desert first. This is especially so since my partner may be thinking along exactly the same lines and may seize the initiative at any moment by deserting me... Genes for deserting FIRST could be favourably selected simply because genes for deserting SECOND would not be.
Let us suppose that females in the ancestral bird of paradise species preferentially went for males with longer than average tails. Provided there was some genetic contribution to the natural variation in male tail length, this would, in time, cause the average tail length of males in the population to increase. Females followed a simple rule: look all the males over and go for the one with the longest tail. Any female who departed from this rule was penalized, EVEN IF tails had already become so long that they actually encumbered males possessing them. This was because any female who didn't produce long tailed some had like chance of one of her sons being regarded as attractive. Like a fashion in women's clothes, or in American car design, the trend toward longer tails too off and gathered its own momentum. It was stopped only when tails became so grotesquely long that their manifest disadvantages started to outweigh the advantage of sexual attractiveness.
