Telegony is a theory in heredity, holding that offspring can inherit the characteristics of a previous mate of the female parent; thus the child of a widowed or remarried woman might partake of traits of a previous husband. Previous experiments on several species failed to provide any evidence that offspring would inherit any character from their mother's previous mates, but the phenomenon was later discovered in a species of fly.
The term was coined by August Weismann from the Greek words τῆλε (tèle) meaning 'far' and γονος (gonos) meaning 'offspring'. The name may also refer to Odysseus' son Telegonus, who is mentioned in the ancient Greek epic poem Telegony.
The idea of Telegony goes back to Aristotle. It implies that the signs of the individual, not only inherited from his parents, but also from other males, from which his/her mother had a previous pregnancy.
This was part of the resistance to the marriage in 1361 of Edward, the Black Prince, heir to the throne of Edward III of England, with Joan, the Fair Maid of Kent, who had been previously married: their progeny, it was thought, might not be completely of his Plantagenet blood.
Both Schopenhauer and Herbert Spencer found telegony to be a credible theory; it was only conclusively proved wrong with modern understanding of genetics. The concept of telegonic impregnation was expressed in Greek mythology in the origins of Greek heroes.
Such double fatherhood, one father immortal, one mortal, was a familiar feature of Greek heroes like Theseus, who had a human and a divine father, doubly conceived in the same night. By the understanding of sex in antiquity, the mix of semen gave Theseus a combination of divine as well as mortal characteristics; this explained the hero's more-than-human nature. Sometimes in Greek myth the result could be twins, one born divine of a divine father, the other human of a human sire: see Dioscuri. Of a supposed Parnassos, founder of Delphi, Pausanias observes, "Like the other heroes, as they are called, he had two fathers; one they say was the god Poseidon, the human father being Cleopompus."
Telegony, or the more general doctrine of "maternal impressions", was known in Ancient Israel. The book of Genesis describes Jacob inducing goats and sheep in Laban's herds to bear striped and spotted young by placing dark wooden rods with white stripes in their watering troughs.
The Gnostic followers of Valentinius characteristically took the concept from the physiological world into the realm of psychology and spirituality by extending the influence even to the thoughts of the woman. In the Gospel of Philip, a text among those found at Nag Hammadi:
Whomever the woman loves, to him those who are born are like; if her husband, they are like her husband; if an adulterer, they are like the adulterer. Often when a woman sleeps with her husband, but while her heart is with the adulterer with whom she is accustomed to unite, she bears the one whom she bears so that he is like the adulterer."
Understandings in the 19th century and the collapse of the theory
In the 19th century, the most widely credited example was that of Lord Morton’s mare, reported by the distinguished surgeon Sir Everard Home, and cited by Charles Darwin. Lord Morton bred a white mare with a wild quagga stallion, and when he later bred the same mare with a white stallion, the offspring strangely had stripes in the legs, like the quagga.
August Weismann had expressed doubts about the theory earlier and it fell out of scientific favor in the 1890s. A series of experiments by James Cossar Ewart in Scotland and other researchers in Germany and Brazil failed to find any evidence of the phenomenon. Also, the statistician Karl Pearson pointed out that, if telegony was true, later children of the same couple should increasingly resemble their father, which is not the case. Biologists now explain the phenomenon of Lord Morton's mare using dominant and recessive alleles: the result observed by Morton would be explained in modern terms as the display in the offspring of recessive genes inherited, but not displayed, in the mare or the stallion.
In mammals, each sperm has the haploid set of chromosomes and each egg has another haploid set. During the process of fertilization a zygote with the diploid set is produced. This set will be inherited by every somatic cell of a mammal, with exactly half the genetic material coming from the producer of the sperm (the father) and another half from the producer of the egg (the mother). Thus, the myth of telegony is fundamentally incompatible with our knowledge of genetics and the reproductive process. Encyclopedia Britannica stated "All these beliefs, from inheritance of acquired traits to telegony, must now be classed as superstitions."
Nevertheless, telegony influenced late 19th-century racialist discourse: a woman who had once had a child with a non-Aryan man, it was argued, could never have a "pure" Aryan child again. This idea was adopted by the Nazis.
A group from The University of New South Wales has showed telegony to be a true and valid phenomenon for the first time in a species of fly. Their results were presented at the 2013 XIV Congress of the European Society for Evolutionary Biology in Lisbon and the recent Australasian Evolution Society’s conference in Geelong. Earlier, a team of scientists from Oxford, Uppsala and UCL had conducted a similar research and obtained a similar result.
Professor Leonard A. Herzenberg of Stanford University in 1979 for the first time proved that fetal DNA can pass into the mother during pregnancies. Fred Hutchinson Cancer Research Center in 2012 has shown that it is not uncommon for fetal DNA to get through the blood–brain barrier and into the brain of the mother.Leiden University Medical Center in the same year published a result which indicates fetal DNA from previous pregnancies can enter the bodies of younger siblings.In 2013, scientists around the globe demonstrated in animals, the significant effect of incorporating foreign DNA. 
Apart from the above-mentioned, one Chinese scientist has proposed possible molecular mechanisms that may account for the reported cases of telegony. The proposed mechanisms include the penetration of spermatozoa into the somatic tissues of the female genital tract, the incorporation of the DNA released by spermatozoa into maternal somatic cells, the presence of fetal DNA in maternal blood, incorporation of exogenous DNA into somatic cells, presence of fetal cells and fetal DNA in maternal blood and sperm RNA-mediated non-Mendelian inheritance of epigenetic changes.
At the end of the 20th century in Russia’s Orthodox circles, the idea of telegony sprang up again. In 2004, a book "Virginity and Telegony - The Orthodox church and modern science of genetic inversions” came out. According to Pravda, "It is highly likely that the Orthodox church arrived at an idea to employ telegony to make the parish not to break one of the Ten Commandments that prohibits adultery."
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