MadSci Network: General Biology

Re: How similar must two species be for one to carry the fetus of another?

Date: Sat Feb 2 22:41:51 2002
Posted By: Dr. Paramasivam Kumarasamy, Faculty, Zoology, The American College
Area of science: General Biology
ID: 1012110984.Gb

Interspecies mating cannot happen in nature, 

even if it does occur, the progeny is 

sterile. Fertilized eggs which result from an interspecies 

mating, most of the time, can not develop 

into a normal young one. The differences in 

the genetic make up between parent and the 

offspring leads to the rejection of the 

"newly developing embryo" by the maternal 

immune system as it considers this as a 

foreign tissue.

Even if the embryo develops into an young 

one (if the fetus has similar cell surface 

antigens that resemble that of the mother 

and as a conquence NOT rejected by the 

maternal immune system), the animal is

usually sterile (because of chromosomal anomalies).

For example: Hinny is a sterile offspring 

produced through a mating between a male 

horse and a female donkey.

Mules are  produced as a consequence of a 

mating between a male donkey and a female 

horse. Note that these mules are also 


There are many ways by which different 

species of animals are isolated from each 

other and maintained, called as isolating 

mechanisms.( refer "Evolution: Process and 

Product" by E.O.Dodson and P.Dodson,ISBN 

0-442-22164-9 pages 355 - 375)

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