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According to the diversity-repressing theory for the benefit of sex, sex
protects the genetic quality of the species. The diversity-repressing theory envisions
that asexual species accumulate harmful mutations over time and gradually become
less functional, as though asexual lizards gradually lost the ability to run fast
or digest some food. Sex supposedly counteracts this danger by allowing family
lines that have picked up harmful mutations to recombine, producing offspring
free of bad mutations. According to this theory, some offspring will possess both
families' mutations and will die even more quickly, but other offspring will have
none of the mutations, and will prosper on behalf of the species. According to
this theory, without sex each and every family line inexorably accumulates mutations,
leading eventually to species extinction.
Ending the Debate
both the diversity-affirming and diversity-repressing views have a long history,
the time has come for closure. The time has come to reject the diversity-repressing
view as both theoretically impossible and empirically vacuous. The scenario envisioned
by the diversity-repressing theory can't exist. In an asexual species, when a
bad gene arises, the line where the mutation originated is lost to natural selection,
whereas the lines without the mutation prosper. The entire stock never deteriorates,
because natural selection doesn't look the other way while a bad gene spreads.
Instead, natural selection eliminates a bad gene when it first appears, preserving
the overall functionality of the species. No evidence whatsoever shows asexual
species becoming extinct because of a progressive accumulation of disabilities
and loss of functionality. A bad gene never gets going in an asexual species,
and sex's supposed pruning of the gene pool is unnecessary and mythical.
the other hand, the environment does change from year to year, and individuals
who don't do well one year may shine when conditions change, and vice versa. Butterflies
whose enzymes work at cold temperatures thrive in dark, damp years, while butterflies
whose enzymes function best at hot temperatures do better in sunny drought years.
All butterflies are perfectly good butterflies, even if the abilities of some
don't match the opportunities currently supplied by the environment.
don't see any grounds for dignifying the diversity-repressing view for the benefit
of sex as a viable alternative to the diversity-affirming view. To be agreeable,
one might say both theories are valid. But this compromise isn't true. Conceding,
even slightly, that one function of sex is to prune diversity puts forth a view
that hasn't earned its place scientifically. Accepting a diversity-repressing
view of sex simply to be polite admits through the back door a philosophical stance
that may later be used to justify discrimination.
I accept as a working premise that a species' biological rainbow is good-good
because diversity allows a species to survive and prosper in continually changing
conditions. I further accept that the purpose of sex is to maintain the rainbow's
diversity, resynthesizing that diversity each generation in order to continually
rebalance the genetic portfolio of the species. I reject the alternative theory
that sex exists to prune the gene pool of bad diversity.
Darwinists have to
take a consistent stand on the value of diversity. They can't maintain on the
one hand that most variation is good because it's needed for natural selection
and on the other hand also maintain that females must continually shop for males
with the best genes as though most genes could be ranked from good to bad. Instead,
I argue that almost all diversity is good and that female choice is more for the
best match than for the best male.
How then should we assess
the rainbows in our own species? We should be grateful that we do reproduce sexually,
although we probably take this gift for granted. I feel too that we should conserve
and embrace our rainbows. Affirming diversity is hard, very hard. We must come
to accept ourselves and love our neighbors, regardless of color in the rainbow.
sex is essentially cooperative-a natural covenant to share genetic wealth. Sexual
reproduction is not a battle.
-Roughgarden, Joan, Evolution's Rainbow: Diversity,
Gender, and Sexuality in Nature and People, University of California Press Ltd:
Reflection Exercise Explanation
Goal of this Home Study Course is to create a learning experience that enhances
your clinical skills. We encourage you to discuss the Personal Reflection
Journaling Activities, found at the end of each Section, with your colleagues.
Thus, you are provided with an opportunity for a Group Discussion experience.
Case Study examples might include: family background, socio-economic status, education,
occupation, social/emotional issues, legal/financial issues, death/dying/health,
home management, parenting, etc. as you deem appropriate. A Case Study is to be
approximately 250 words in length. However, since the content of these Personal
Reflection Journaling Exercises is intended for your future reference, they
may contain confidential information and are to be applied as a work in
progress. You will not
be required to provide us with these Journaling Activities.
Reflection Exercise #1
The preceding section contained information
about the "Diversity-Repressing" theory. . Write three case study examples
regarding how you might use the content of this section in your practice.
According to the diversity-repressing theory, what is the benefit
of sex? To select and enter your answer go to .