Competition for mates between prehistoric human women may have contributed to 'concealed ovulation' – a lack of any notable physical clues that a woman is fertile, experts say. Using computational ...

The following references illustrate the fact that a new human embryo, the starting point for a human life, comes into existence with the formation of the one-celled zygote: "Development of the embryo ...

A human egg has been filmed in close-up emerging from the ovary for the first time, captured by chance during a routine operation. Fertile women release one or more eggs every month, but until now, ...

SCIENTISTS have created the first human embryos in Britain by a technique of 'virgin conception' that does not involve either fertilisation with sperm or cloning. The six embryos lived for between ...

"Chimeras are the result of fusion of two zygotes to form a single embryo, producing an individual with genetically different kinds of tissue. If the fused zygotes are of different sex, the individual ...

Twins occur in about one out of 90 human pregnancies in the US. As a rule, at conception, one sperm fertilizes a single egg to produce a zygote. Two thirds of twins are fraternal, with fertilization ...