[extropy-chat] Hybrids

Fri Jan 30 00:08:54 UTC 2004

I was involved in the attempting to develop a marketable Bison Hybrid back in the
1970's.
Many unforseen issues can arise.  In the case of bison - bovine hybrids there was a
dramatic difference between male and female offspring.  The F1 and F2 male offspring
were usually infertile and had under developed testes.  The females were quite
normal at any generation.  Usually bovine females were bred to bison to begin the
process.  The male fetuses caused severe immunological reactions in the mother.
The uterus greatly inflated blocking off the other organs of the bovine mother.
This caused starvation in some cases.  Abortion and early birth with complications
such as immature lungs without surfactants caused widespread mortality of
predominantly male offspring.  The fluid issue was referred to as Hydrops.
We had calves born 1-2 months premature who had these problems and died within 1 day
or 2 of birth.  Usually one could sex the offspring just by noting which cows were
building up fluid.  Males caused much more Hydrops than females.

When one used hybrid mothers, there was much less of the extreme incompatibility,
however gestation was many times a month earlier than for bovines.

Recombination did eventually produce some 30-45% fertile males to continue the
breeding with.  The merchandising of the meat was not highly successful so the
breeder market has largely disappeared.  From 1965-1985 there was however much
activity in this area.

So,  the bison/bovine divergence marks the limit under natural conditions under
which mating can be successful.

Bison hybrids would be an ideal research tool to investigate this further, given
that the tools available to entrepreneurial ranchers of the 1970's are far less than
the state of today's art.

Morris Johnson

Anders Sandberg wrote:

> David Lubkin said:
> > No one responded to the question I posed a couple weeks ago, so I'll ask
> > again. It was asked in a reply to a religious thread, so many people may
> > have missed it.
> >
> >>How is it that a horse and a donkey -- different species, with different
> >>numbers of chromosomes -- can produce offspring?  What are the limits of
> >>cross-species mating, besides incompatible hardware, e.g., horse and
> >>gerbil?  Given species x, y and gestational periods g(x) and g(y),
> >>respectively, what will the gestational period of an x carrying an x/y
> >>hybrid be?
>
> A fast google:
> http://gslc.genetics.utah.edu/units/basics/conservation/tools/chromoanalysis.cfm
>
> "For the mule, having parents with different chromosome numbers isn't a
> problem. During mitotic cell division, each of the chromosomes copies
> itself and then distributes these two copies to the two daughter cells. In
> contrast, when the mule is producing sperm or egg cells during meiosis,
> each pair of chromosomes (one from Mom and one from Dad) need to pair up
> with each other. Since the mule doesn't have an even number of homologous
> pairs (his parents had different chromosome numbers), meiosis is disrupted
> and viable sperm and eggs are not formed."
>
> Seems there are plenty of possible hybrids:
> http://members.aol.com/jshartwell/hybrid-mammals.html
> That page also has plenty of useful info about when hybrids can occur near
> the end.
>
> In short, I guess you need fairly closely related species since the
> control programs among the genes otherwise may have shifted meanings, and
> the different chromosomes will be sending contradictory orders during
> development.
>
> At least in Bison-Buffalo gestation length become highly variable due to
> hybrids:
> http://www.beefalobeef.com/hybrids.htm
>
> > Beyond being interesting in their own rights, the limits of genetic
> > differences that will produce fertile offspring without technological
> > assistance are an important consideration in forthcoming human genemods.
> >
> > Just as I want some people living off-Earth in an environment that can be
> > viably self-sufficient with primitive technology, I would prefer that
> > humans not fracture into reproductively incompatible successor species.
>
> If you follow Greg Stock's idea with putting the modified genes on an
> extra non-inheritable chromosome this won't be a problem. Even two heavily
> modified parents will have "natural" children - if they want to upgrade
> them, they have to do it at an IVF clinic.
>
> Then again, why is it bad to become a bunch of species? If a society can
> create genetic modifications to create such a situation, then it can also
> be remedied. In a loss of technology scenario where such abilities are
> lost, then the loss of ability is likely a far larger issue than
> reproduction.
>
> --
> Anders Sandberg
> http://www.nada.kth.se/~asa
> http://www.aleph.se/andart/
>
> The sum of human knowledge sounds nice. But I want more.
>
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