Mating Different Species
Can mammals of different species
interbreed. Obviously certain physical charteristics would prevent this.
But, is it possible for example for a cow and a horse to mate and have
offspring. If its not possible ....why????
The classical example of interspecies breeding is
ofcourse the mule, from a horse and a donkey. Other
examples are tigers breeding with lions to produce
'ligers', and sheep with goats. In all of these cases
the species are close enough to allow breeding, but
the offspring is sterile (I am sure about the mule,not
about the others). Other than behavioural difficulties
(do they understand each others 'courting' language?)
there are important biolgogical restrictions at the
DNA level for interspecies breeding. The chromosomes
of the sperm and egg cell have to match sufficiently
to start deviding. So the two species must be
genetically close enough. Beside genes the DNA
contains many repeated sequences, that have not
meaning as far as we know, and these seem to be
involved in determining the genetic match. There is
still a lot of research done in this area.
There are sooo many barriers and considerations to realize.
Behavior differences (different species do not have the same behaviors
required to creating the mating behaviors.
Physical (structural) differences ( the mating apparatus must be compatible
to both sexes.
Chromosome number differences (This is the key! They have to pair up to
operate and if you are dealing with different numbers or different traits
in the same location, NOTHING will develop!
Internal chemistry differences ( timing of mating season, timing of
fertilization, chemistry needed to penetrate the egg, etc.
Sperm enzyme differences (similar to above for the sperm must have the
right enzymes to penetrate the egg to fertilize.
Chemical signaling differences (This is complex but it is essential the
Internal Chemistry differences)
Immune system differences in response to foreign bodies (sperm is a foreign
These are just off the top of my head. All of these are significant in a
The strict definition of species is NO. But there are noted exceptions. It
depends how far separated in evolution the species are. It is believed that
all dogs descended from a wolf-like species and dogs and wolves have been
known to interbreed. Usually though, even if two different species
interbreed and produce offspring, THEIR offspring cannot produce offspring.
An example is the mating of a horse and a donkey. The outcome is a mule and
mules are sterile. The only way to get more mules is to mate horses and
donkeys again. One of the barriers seems to be that different species have
different numbers of chromosomes and they would not pair up evenly at
meiosis. So for example chimps and humans are very close together in the
amount of DNA, but chimps have 48 chromosomes and humans have 46.
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Update: June 2012