Why are twins,triplets,quadruplets so rare amongst human beings but so common amongst dogs,cats,tigers etc?

I think because of our genetics ans evulution and they have a higher risks of losing thier babies than we do.

Because it dose not happen as much.

1. We spend more time and energy looking after our young and so biolgically we have less than say fish etc which have screes. In fact we spend more time looking after young than any other species. 2. As we are bipedal, our hips, pelvis etc are positioned in such a way that it makes birth more dangerous than pretty much any other animal (as we have them "more premature" as a result ) to allow their heads to fit in the birth canal. So having more than 1 baby at a time is even more dangerous. 3. Cats are actually quite prolific breeders and like rabbits etc will release several eggs at ovulation, rather than our usual 1. This means that several sperm will fertilise the several eggs and produce offspring no more related than other offspring produced by the same parents. Females can also release 2 eggs at ovulation and they can be fertilised by 2 sperm to produce FRATERNAL or non-identical twins and again are genetically the same as other brothers and sisters born at different times. Many of the multiple birhts today are the resule of fertility treatment which causes the ovary to release several eggs in the hope of getting 1 fertilised. Identical twins/triplets are when 1 egg and 1 sperm fertilise and the resulting zygote starts to divide. For some reason (unknown) this group of cells divides (twins) and may do it again (identical triplets, quads etc). These cells at this stage are stem cells, in that they can turn into anything (they don't differentiate into specific organs until later) so you don't miss arms/legs etc as a result. Many other animals usually have more than 1 offspring like we do, but they are better equiped for it than we are (biologically speaking)

Identical twins are the result of the fertilization and then the splitting of one egg. So they are two parts of one whole growing into individual but identical babies. The sex will be the same...two girls or two boys and they will be identical because the genetic makeup is the same. Non identical twins, triplets, quadruplets in humans are the result of two or more eggs being fertilized at the same time. Thereby growing and looking as different as any other brother and sister Animals such as all dogs, all cats, pigs, rabbits, rats that are designed to have more than one baby have LITTERS. And sometimes they can have a set of identical twins in their litters. It seems like the number of babies that an animal can have is directly related to the number of faucets "nipples" that they have to be able to feed the babies. I raise pigs. They have anywhere from 5 to 18 and more piglets in a litter. Some of the piglets have their own placentas. These are usually the ones that are the biggest in the litter. I have seen as high as 5 piglets with individual birth sacs share one placenta. I found this out when I started counting placentas with the hope of determining whether or not the sow had cleared her uterus of all material after she was done birthing her babies. If the sow doesn't thoroughly clean out after giving birth she can get very ill and she will not produce milk very well for her babies. Actually the same is true for ANY animal, humans included, that retains any of the placenta material. Infection will set in and death can occur if treatment isn't immediately sought.

Because twins, triplets, quadruplets are not so common among humans because their organs are made that way. A limited amount of sperm can form a baby which when increases in a single time, twins are produced or even more. Dogs, cats etc. cross with many other dogs & form a complex sperm which generates to a new kind of baby, often twins or triplets.