Re: can you put a female dog egg into a female human womb?

Could a dog fetus develop inside a human womb?

The introduction of a dog oocyte (egg cell) into a human uterus is a 
technical matter, and I don’t see why that wouldn’t be possible. What 
happens next is the tricky part – could the dog oocyte be fertilized and 
then develop. I don’t know that anyone has ever tried this experiment, 
but I don’t think it would work. 

One of the things that make species different is the establishment of 
reproductive isolating mechanisms. This means that biochemistries and 
behaviors evolve to prevent gene exchange between the two groups. In 
levels of increasing effectiveness, these isolating mechanisms mean that:
(1) the offspring produced between two different species will not be 
fertile, and therefore unable to have offspring of its own,
(2) the two species will not find each other sexually attractive, or will 
have other mechanisms that prevent interbreeding such as incompatible 
parts or breeding seasons

These two mechanisms can also have equivalents on the microscopic level, 
so that:
(1) the developmental requirements of the embryo are not compatible with 
the biological environment of the uterus.
(2) the biochemistry of the two germ cells are so different that sperm is 
unable to penetrate the oocyte, or may not even recognize it as an oocyte.

Because humans and dogs are different species several of these isolating 
mechanisms come into play. If you overcome the fertilization issue and 
introduce a growing embryo into a human uterus it still wouldn’t work. 
Many mammals have different types of implantation mechanisms. 
Implantation is the technical term for how the embryo attaches itself to 
the uterus. In humans the embryo actually buries itself into the wall of 
the uterus. Human biology is set up to support only this type of 
implantation. The dog, and many other animals that give birth to litters, 
uses a superficial implantation. The embryo attaches itself to the 
surface of the inside wall of the uterus, it does not bury itself into 
the wall of the uterus. Because of these differences, a dog embryo 
wouldn’t “know” how to grow inside the human uterus, and the human uterus 
wouldn’t “know” nurture the growth of the dog embryo. So, it wouldn’t 
work.

There are experiments where embryos are successfully implanted into 
closely related species. But for this to work the biochemistry of 
development has to be very similar. Humans and dogs are so distantly 
related that I doubt that this process would work.