I did my master's thesis on twin research methodology since you asked. Very interesting stuff. The effects of the environment and genetics on a range of outcomes such as language and brain development, physical development motor control, criminality, statistical probabilities in the medical field like smoking and cancer rates, obesity. Twins are used to determine things like does smoking cause cancer? Are some people naturally fat? Get diabetes? Have learning disabilities due to genetic factors? How does abuse or an absent father or baby Einstein videos affect children and adults? Twins are used to measure rate of change over time as a genetically perfect control and experiment group. A big part of these studies are studies in gender. Boy/girl DZ twins are used in childhood development studies to determine gender specific behavior. For example you can put infant with novel gendered toys and track durration of eye movement and stay rates. The data is collected and statistically analized. These studies shape policy, medical practices, educational programs etc. So that is why i pointed to my boy girl twins. It is why i took an intrest in the subject. I walked into.my degree believing what i had always been told... That boys and girls were the same and were shaped differently by their environment their parents their peers society. And i left knowing that that was just the bullshit lie we have all been told so we can buy into equality. Some things are shaped by the environment but many are not. Boys and girls are different. From before birth. From conception. Their brains are different. Their bodys are different. The way they solve problems and approach tasks and feel about things are different. They are different. Different in a good way. Differently specialized through millions of years of evolution. Boys dont have good fine motor skills arent flexible dont have as large of a language processing or speech area in their brain (barocas and wernikies area-maybe i spelled that wrong) we can see things like 7% of men qualify as illiterate and only 4% of women. We can see that autism affects 4x as many men than women. men do not process feelings the way we do dont orgasm like we do, not feel the need to emotionally bond during sex they have testosterone which gives them more muscle and aggression. We can scientifically test these things. We know that we can give people steroids or testosterone and it will increase muscle mass and aggression. We can give a man estrogen and hell grow tits and feel more emotional. But we can not even begin to play with this info can not use it to better ourselves if we look at the facts facts and deny them. We can not begin to genetically engineer people yes i said it- i welcome disease/disability free genetically engineered babies or eradicate disease or just design better programs for people if we can not understand who we are as people and where we come from. And no lol im on my phone on my bed. And my poor grammer does not negate my point. -i started 2 sentences with and in a row just for you