[EVA] Inbreeding (Ugh! was: Marduck and my fanfic.)

[Gareth Ortiz]

I hope I cited everyone correctly... ^_^;;

 Gnollman Wrote:

>This is called an inbreeding barrier, or inbreeding depression.  However,
>over time, the barrier is surmounted as the lethal traits are purged
>through selection, and a genetically fit, though possibly altered, form
>does arise.

From: Christopher G. Eckert Department of Biology Queen's University

"Inbreeding depression can be defined as the reduction in fitness of 
offspring derived from mating between relatives (inbreeding) compared to
offspring resulting from mating among unrelated individuals (outcrossing).
The harmful effects of close inbreeding were widely recognized well before
any formal scientific investigation into the phenomenon. Indeed, in humans
about 42% of offspring from sister-brother marriages die before they reach
reproductive age, hence most, though not all, cultures have strong
traditions with respect to incest."

From: Mark W. Courtney of Chicago Zoological Soc

"In natural populations, inbreeding commonly results in offspring with
more frequent birth defects, higher mortality, slower growth, lower
fertility, lesser disease resistance, and/or other aspects of reduced
fitness.  This phenomenon, termed "inbreeding depression", is almost
universal."
"As increasingly many natural populations are reduced to small, isolated
fragments, inbreeding may become common in remnant populations.  Whether
populations can adapt to such conditions and recover or will suffer an
inevitable decline in fitness will be determined by the still unknown
number and nature of genes that contribute to inbreeding depression."

From: Gregory McCants of ASU 

"The conservation of endangered species often hinges on the avoidance of
inbreeding depression or the retention of genetic variation."

From: Dr. Barry Sinervo, Professor of Animal Behavior at UCSC

"The effects of reduced survival in inbred individuals were most strongly
manifest during periods of environmental stress.  Moreover, each
sub-population has a modest probability of local extinction where all
members of the population might be eliminated by some random environmental
disaster."

"According to Dr. Diana Bianchi, of the Medical Genetics program at Tufts 
University Medical School, the genetic risks may actually be quite high.
She cited a study of parent-child and brother-sister incest showing a rate
of genetic abnormalities of 43%. Another article revealed a higher than
expected incidence of abnormal neuropsychiatric findings among twenty-two 
patients who were the child or younger member of an incestuous 
relationship; e.g., a higher incidence of seizures and lower IQ
(International Journal of Psychiatry & Medicine, 1978-79; 9(2):117-21)"

This is from an ABC news article:

"Finnish biologists have proven what conservationists have long suspected,
that inbreeding can lead to the extinction of endangered species.  In a
study published today in the scientific journal Nature, Ilik Saccheri and
Ilkka Hanski of the University of Helsinki used DNA analysis on a breed of
wild butterflies to show that a loss of genetic variation increases risk
of extinction. The biologists found that risk of extinction increased
significantly with decreasing gene diversity, an indication of inbreeding,
even after accounting for the effects of ecological factors such as
climate, disease and availability of food.  Zoologist Katherine Ralls, of
the Smithsonian Institution in Washington and Australian biologist Richard
Frankham said in an accompanying commentary that the Finnish study was the
first direct evidence that inbreeding is linked to extinction.  The
results of the study, they added, can be extended to other species and
show that genetics may be a factor in making island populations prone to
extinction."

I hope you got the point.  Most of these studies which link inbreeding to
extinction are operating on populations far larger than one member of each
sex, and they are operating in controlled environments.  The odds against 
a race developing from two individuals (automatically resulting in a weak
genetic pool to start with due to a lack of variety...two people simply
can't possess enough genetic variation even being completely unrelated)
are astronomical even in a controlled environment.  In the wild, where all
kinds of environmental misfortunes may occur even under the best of
circumstances, extinction is effectively assured.  Add to this the fact 
that the world at the end of EOE is under  tremendous evironmental stress
following the third impact and well...

Later,

Gareth