When humans inbreed with family it has a greater chance of deformation...

is this the same case with most other species? i dont see why it would only effect one...

just curious. feels weird asking this, but when i get a curiosity in my mind, i really want to learn the answer.

In most animal breeding it is very common, and is sometimes called "line breeding". If it doesn't work, it is called "inbreeding." Animal breeders can get away with it by using culling. the deformed or useless ones are killed or not used for further breeding.

When this is done with people, it is called "eugenics" ("good breeding") and consists of selection of mating pair by "authorities" and of culling or sterilisation. This was a social programme in common practise between perhaps 1890 to 1960, and included forced sterilisation of "undesirable" groups of people..

Any time an animal breeds with a close relative there is an increased chance that a recessive genetic mutation will present in the offspring. In the case of unrelated parents, one parent may have a recessive mutation (recessive meaning that it would only show up if the individual had two mutant copies, as humans have two copies of each gene) but the chances that the other parent would also carry the same recessive mutation would be much smaller than if they were from the same family and shared much of the same genes. This is why in humans that inbreed there is an increased chance of there being some sort of defect in the offspring. For example, you can look back at the old European royal families (that only bred with their own kind) and see increased incidence of things like dwarfism.

This does happen in animals other than humans for the same reasons. Purebred dogs, for example, often have increased incidence of certain diseases (hip dysplasia, for example) than mutts.

In general, most mammal species have evolved to avoid inbreeding. When inbreeding does occur, the incidence of defects such as low birth weight, neonatal mortality, and recessive genetic diseases is much higher.

In humans, the birth defect rate for the children of consanguineous first cousins is 3-4% higher than those of unrelated parents; this accounts for over 10,000 birth defects and stillbirths in the US each year.

This is only an unproven hypothesis. Personally I believe this is false.