Pat asks:

>Does anyone know why there are not more hermaphrodite species,
>according to evolutionary theory?  Seems like a hermaphrodite species
>could achieve most of the advantages of a diverse gene pool (assuming
>the individual can not mate with itself) while being much more
>efficient with resources.

This is a very reasonable question, but given the paucity of obligately outbred
hemaphroditic species in nature, evolution must clearly have found substantial
advantage in the invention and exaggeration of gender.

The reason for that invention may lie in a completely unexpected answer: the
suppression of germline error. The rates of error infusion into germline DNA
are not trivial. Without the invention of mechanisms to identify that error and
expunge it from the germline, that error will only continue to accumulate,
constantly degrading the competitiveness of the species until finally it
reaches the point of quiescing the species's capacity to continue.

The only universal criterion that can be used to identify the male gender is
the size of its gametes. When anisogamy (differently sized gametes) is present,
as it is in virtually all plant and animal species, the smaller gametic gender
is declared the male. This smaller size intrinsically allows the male gender to
produce more gametes, spread them more widely, and tolerate more failures to
inseminate an egg, simply because the "investment" in any one
gamete is so much
smaller than that of the macrogametic gender's investment in its eggs.

But this difference in gametic investment also allows evolution to exaggerate
gender-specific differences in the behavior of the adult male as well, making
it inherently more error expositive, more sacrificial and more combative than
the species's female. By doing this, the species appears to be testing the
male's lack of primary congenital defects prior to mating, allowing the male to
act as an filter of gene defects without imposing an equal cost on the
mother-daughter line of descent.

If you wish to read more on this form of explanation, please see:

     http://aics-research.com/research/males1.html

The rate of error infusion into a germline is not trivial. If the species is to
outlive its cells, then some mechanism of error identification and expurgation
must be invented and imposed on the transmission of germline DNA, generation to
generation. If the species remains hermaphroditic, then all individuals must be
forced to run some sort of gauntlet to demonstrate their absence of significant
congenital defects prior to mating. But if the species partitions itself into
two gender castes, then only one of those genders need be put at substantial
risk in order to demonstrate its lack of defects.

Wirt Atmar
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