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... some evidence suggests human females also undergo semi-annual heat cycles. Although sexual responsiveness is influenced by social and cultural factors, there is evidence that human females undergo emotional and physiological changes associated with estrus cycles and may be more likely to be irritable and/or sexually aroused during the peaks of heat cycles. Further, just as males of other species respond in differing ways to females in...
 sex human heat estrus female cycle reproduction heat cycle
People who live in the tropics have more baby girls compared with those living in other parts of the world.

2009-04-01

 gender geography reproduction climate
Virgin births do occur among animals. Many invertebrates, such as insects, can produce offspring asexually, without ever having mated. They usually do this by cloning themselves, producing genetically identical offspring. But among vertebrate animals, it remains a novelty, having been documented among less than 0.1% of vertebrate species.

2010-11-03

 snake virgin birth sex Virgin Mary reproduction mating cloning immaculate conception conception
Worms forced to reproduce asexually succumbed to a nasty bacterial infection and died. The researchers say the results are the most convincing evidence to date for a key theory in evolutionary biology. The theory holds that sex evolved because it lets organisms reshuffle their genes into new combinations to stay a step ahead of parasites.

2011-07-08

 worm sex reproduction evolution asexual cloning biology parasite resistance
Stick insects have lived for one million years without sex, genetic research has revealed.

2011-07-19

 insect asexual sex virgin birth evolution reproduction biology
If early humans had been vegans we might all still be living in caves, Swedish researchers suggested in an article Thursday. When a mother eats meat, her breast-fed child's brain grows faster and she is able to wean the child at an earlier age, allowing her to have more children faster, the article explains. That provided a distinct competitive advantage for early humans when limited resources and a small population made it difficult...

2012-04-20

 meat breastfeeding child offspring evolution human evolution reproduction