...a Mayan. Wow, he really was gonna go back a long time, Ty realized. Time had turned back not just hundreds but thousands of years for him just now, and he could tell it would be interesting to say the least.
Ty decided to age himself to birth and make himself aware of the culture he'd be born into and the person he'd be as he developed. A few things came to him instantly as his xygote self began to grow- he saw a city-state in Mesoamerica over 2600 years ago which was to be his home in this new life, and his self-perception changed to fit his new self as his skin tone darkened and knowledge of the Yucatec language developed in his head.
Slowly Ty realized something else felt different now that had nothing to do with the culture which he would be born into. It felt like something was different in his body. He couldn't place it, so he wished to know what it was, and the answer surprised him- the sperm of the Mayan man who was to be Ty's father that had fertilized his egg form had had an X chromosome instead of a Y.
Right after Ty realized this, his body reached the point of developing its sex characteristics, and he saw and felt his body's form change from male to female. His figure grew more petite and less muscular; his facial structure reshaped and his skin smoothed; his shoulders moved inwards and his hips pushed outwards to child-bearing proportions; his chest swelled with large, soft flesh as her breasts developed and the nipples grew wider and more sensitive; his penis receded away inside him and the head formed her clitoris; his testicles tucked up inside him and changed into her ovaries while his scrotum formed into her vaginal lips.
Ty felt astonished at how her feminized self looked and felt, but to her surprise she kinda accepted it. She was already gonna be a Mayan, may as well be a girl too, she figured.
After a minute or so getting used to her new self, she saw a bright light crack open before her, and loud groaning and yelling as something pushed at her. She emerged from the Mayan woman who was now her mother's pussy, a newborn Mayan baby.