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It would also provide a sober, drug-free and nonsmoking carrier that is less expensive than human surrogates. [3] For animals, it could be a valuable tool in preservation programs of endangered species, providing a method of ex situ conservation. [4] [5] It could also avail for recreation of extinct species.
The possibility of hybrids between humans and other apes has been entertained since at least the medieval period; Saint Peter Damian (11th century) claimed to have been told of the offspring of a human woman who had mated with an ape, [3] and so did Antonio Zucchelli, an Italian Franciscan capuchin friar who was a missionary in Africa from 1698 to 1702, [4] and Sir Edward Coke in "The ...
Humans, unlike most other species, have concealed ovulation, a lack of obvious external signs to signal estral receptivity at ovulation (i.e., the ability to become pregnant). Some species of animals with estrous cycles have unmistakable outward displays of receptivity, ranging from engorged and colorful genitals to behavioral changes like ...
Heteropaternal superfecundation is common in animals such as cats and dogs. Stray dogs can produce litters in which every puppy has a different sire. Though rare in humans, cases have been documented. In one study on humans, the frequency was 2.4% among dizygotic twins whose parents had been involved in paternity suits. [6]
A pregnant lioness. In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it leaves the uterus.
Pregnant male seahorse. Male pregnancy is the incubation of one or more embryos or fetuses by organisms of the male sex in some species. Most species that reproduce by sexual reproduction are heterogamous—females producing larger gametes and males producing smaller gametes ().
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Superfetation (also spelled superfoetation – see fetus) is the simultaneous occurrence of more than one stage of developing offspring in the same animal. [1] [2] [3]In mammals, it manifests as the formation of an embryo from a subsequent menstrual cycle, while another embryo or fetus is already present in the uterus.