Second, people wonder if genes or the environment will effects twins more. People compare MZ twins reared together with those separated at birth and raised in different families. Similarity, twins reared together affect both genes and environment. Similarly twins reared apart are affected by only genes because they don’t share experiences together. Most of people would guess that twins reared together would be more alike than twins reared apart. But are they? From a research, I got an answer that an MZ twin reared away from his or her co-twin seems to have about as much similar as the co-twin who has been reared together in terms of personality, interests, and attitudes. This leads us to believe that the similarities between twins are due to genes, not the environment.

Next, there are 7 characteristics that increase the chances for  women having twins. They are: taller than average, large bone structure and carrying a little extra weight; African – American; older age in childbearing (30 years or more); on birth control for several years; fraternal twins in the family; use on fertility techniques; being a fraternal twin which will cause an increasing chance by 5 fold.

 At last, there are some interesting rates of twins. In 1997, 2.6% of births were twins. Another data shows that one in 50,000 births results in conjoined twins. The following is about some data of fraternal twinning by racial background:

Ø       Japanese 1 in 150 births;

Anyway, the studying of twins still has a long ways to go. It will help us to determine how genes and environment influence our life, but science still cannot yet explain all the facts of twins.