As children they watched the same television programs. All of this is surprising because they were separated at birth, were raised by different families, and did not meet until they were age 31.
On meeting for the first time, their physical resemblance is striking. As they spend time together and share their life stories, similarities of behavior also become evident. How they walk and even held a beer are the same. They learn that they share the same hobby of white-water rafting and even the same occupation. Why do we have these striking similarities, ask the twins? They conclude it must be the result of shared genes.
Indeed, studies of identical twins separated at birth have helped shift scientific thinking toward a greater appreciation of genetic influences. Jerry and Mark are not unique in demonstrating startling similarities of personalities, abilities, interests, and even fears.
As you watch this video you should be aware that some critics remain unconvinced that such case studies establish the importance of genetic influence. They argue that any two strangers who spend considerable time together comparing their behaviors and life histories are likely to discover many coincidental similarities.