The two genders are complimentary and that is how they work best. Men don't go through a menstrual cycle or have babies, and men don't naturally get breasts that are used to feed babies.
The organs of men and women have some critical differences all to function for procreation. If procreation wasn't the object of the differences, then there wouldn't be any differences between men and women.
The hormones and the wiring in the brains are different between men and women, again to serve a common purpose.
Procreation is not mandatory for each person, but it is not possible without a contribution from each gender.
The simplest thing DNA can tell you is whether someone is male or female. Apart from some very rare cases, that doesn't even involve looking at their DNA sequence - all you need to know is whether they have X and Y chromosomes (making them male) or a pair of Xs (which makes them female).
That should be the answer for gender.
In the animal kingdom, they observe the survival of the fittest to get the strongest genes, while humans don't filter the genes, anyone that can have sex can pass on their genes.
In doing so we have allowed bad genes into the pool, and that is because we are not animals. The result however has caused passing susceptibility of diseases, handicaps, and mixed wiring of genders.
In the past 60 years, the profit makers that supply our food have clouded our bodies and minds with non food products that are bodies have no idea how to handle. Free radicals attack the cells in our bodies until they malfunction, and that is from fatty foods.
As our diets changed, so did we change, and not for the better. Our immune systems lose integrity battling all the new foods, and our changing environment.
While homosexuality existed in the earliest times, I believe that the reasons were based on their society rather than on nature.
The natural law is bisexual for the purpose of procreation. DNA determines gender, but changes to the DNA can create anomalies that shunt the natural law making it non functioning.