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The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. [5] The Yoruba people have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, [6] [7] [8] possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may ...
Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse, which can lead to twin babies from two separate biological fathers. [ 1 ] [ 2 ] The term superfecundation is derived from fecund , meaning able to produce offspring.
This rare occurrence, when twins have the same mother but different fathers, is called superfecundation. This case is thought to be the first set of bi-paternal twins born in Vietnam, though there ...
A fraternal twin is a sibling and, therefore, is related by 50% consanguinity. [26] Fraternal twins are no more genetically similar than regular siblings. As identical twins come from the same zygote, their most recent common ancestor is each other.
One of the twins (Polydeuces, Heracles) is the illegitimate son of the god Zeus; his brother is the son of their mother's mortal husband. A similar pair of twin sisters are Helen (of Troy) and Clytemnestra (who are also sisters of Castor and Polydeuces). The theme occurs in other mythologies as well, and is called superfecundation.
Bilateral descent is a form of kinship system in which an individual's family membership derives from and is traced through both the paternal and maternal sides. The relatives on the mother's side and father's side are equally important for emotional ties or for transfer of property or wealth.
The Paternal Care hypothesis: Paternal care and investment will be designated to biological offspring, increasing the infant's chance of survival, and therefore increasing the male's own fitness. [ 33 ] [ 27 ] This hypothesis requires the on male to use recognition and behavioural cues to distinguish their own offspring from other infants. [ 29 ]
This is because mammals have imprinted genetic regions, where either the maternal or the paternal chromosome is inactivated in the offspring for development to proceed normally. A mammal developing from parthenogenesis would have double doses of maternally imprinted genes and lack paternally imprinted genes, leading to developmental abnormalities.