IIs it natural to be able to choose your gender? Is our gender biologically determined or is it a social construct?
Boys and Girls
I remember years ago a guest speaker coming to a church I used to attend and telling us about an interesting study a psychologist did. He wanted to prove that boys and girls are the way they are because of their social conditioning and environment, being shaped and molded by their surroundings, so to prove his point, he went to a preschool and offered to help the school with some funds if he could do a harmless study on the nature and characteristics of boys and girls. He separated the preschool boys and the girls, making sure their teacher was still in the room, but he put the boys in one room and the girls in another. This one-day study was for about 3 hours. For the boys, he only gave them dolls to play with and nothing else besides books. For the girls, all they had were trucks and boy books. He was trying to prove that the boy-centered toys, like trucks, would make the girls play with trucks just like the boys did (making zooming sounds like a truck would), and he also wanted to prove that girl-centered toys like dolls, would make the boys play more like girls (nurturing the dolls, feeding them, etc.). After the 3 hours were up, the psychologist entered the boys room and found that the boys had torn the heads off the dolls and taken the dolls eyes out (under supervision of course) and were playing with them. When the psychologist walked into the room where the girls were playing with trucks, one little girl stopped him at the door and said, “Shhh! We just put the trucks to sleep.” There lying on the floor, he saw the trucks were all bundled up in a blanket, taking a nap! The point this psychologist was trying to make about boys and girls are masculine or feminine only because of their environment, backfired on him. The conclusion; boys are boys and girls are girls, because that’s the way God wired them, so why do parents allow their children to make choices as to their gender identity when God’s already determined it? 
To be male or female is not a choice of ours, but a choice God has made, even before we were conceived. He called Jeremiah by name before he was born, so it is wrong to ask a young child what gender they prefer to be. First of all, they are not in any position to decide such a thing. They are not mature enough to make those kind of choices. Besides, the choice has already been made, so it’s not their choice but God’s. Sadly, many gender-neutral parents are raising their young children by encouraging them to be whatever sex they want to be. That’s far too much empowerment to give a young child, because they’re too young to understand the ramifications. Sometimes parents even push a child into having a preference for a gender that’s not naturally their own. For example, some parents now let their boys wear makeup, girls clothes, put on wigs, and so on, but not so much to encourage the young child to “explore their gender” but to almost have a personal agenda in promoting it. One of the civil laws in ancient Israel was that “A woman shall not wear a man’s garment, nor shall a man put on a woman’s cloak, for whoever does these things is an abomination to the LORD your God” (Deut 22:5), and since it is sin to dress like someone of the opposite sex, how much worse is it to have a sex change that goes beyond clothing!?
A recent scientific study concluded that gender differences in toy choice exists, and it appears to be the product of both innate and social forces, and despite methodological variation in the choice and number of toys offered, context of testing, and age of child, the consistency in finding sex differences in children’s preferences for toys typed to their own gender indicates the likelihood that their gender has a biological origin. Also, the time playing with male‐typed toys increased as boys got older, but the same pattern was not found in girls. This seems to indicate that stereotypical social effects may persist longer for boys, or that there are stronger biological predispositions for certain play styles in boys. Even from an early age, most children choose toys that are typed to their own gender. Boys will naturally play with trucks about 90% of the time when offered a truck or a doll, while girls overwhelmingly preferred dolls over trucks.
Male and Female
It says in the creation account that “God created man in his own image, in the image of God he created him; male and female he created them” (Gen 1:27), so according to Scripture, our gender was decided by God and not by our biological makeup or the social construct we were born into. For those advocating that it’s all about the environment, remember that Adam and Eve had the perfect environment and they still chose to sin, so it’s not about the environment or social setting you live in and are raised in; it is what God made you to be and not what we ourselves chose to be. Our gender is not our choice to make but it is a choice God has already made. You are either male or female. Of course, some are born with both male and female characteristics. An infant born with both ovaries and testicles and has both male and female sex organs is called a hermaphrodite. About one in 2,000 newborns are born into an intersexual state, but this is due to chromosomal or sex hormone abnormalities, and of course the child had no choice in the matter, so it is God Who creates both male and female, and both are created in the image of God, and this image is not to be changed, either by surgery, hormones, or other unnatural means. God knew what He was doing. The Psalmist said, “I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well” (Psalm 139:14).
The liberal social agenda today of wanting to let children or adults have the freedom to choose what sex they want to be, is contrary to scientific studies and evidence, but more importantly, it’s contrary to biblical doctrine. God created us as male and female, and it was He and not we that made this choice. It’s not something we can change or choose because we “feel like it.” God created us as it pleased Him, and it’s not left up to us to choose. Besides, mankind has a bad history in choosing what is good. The forbidden food in the Garden looked good, it may have even smelled good and felt good to the touch, but so does antifreeze to a thirsty dog, meaning, the consequences can be fatal. Jeremiah the Prophet nailed it by saying, “I know, O LORD, that the way of man is not in himself, that it is not in man who walks to direct his steps” (Jer 10:23), so “In all your ways acknowledge him, and he will make straight your paths” (Prov 3:6), and “Be not wise in your own eyes; fear the LORD, and turn away from evil” (Prov 3:7).
Here is some related reading for you: Can a Person be Born a Homosexual? A Bible Study 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible: English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.