Readin the Christian Bible. That covers the time from their creation through the fall in temptation for which God cast them out of the Garden of Eden, after which they had sex and conceived children. The timeline seems rather short for them to have been created with infant bodies, not to mention that they had no parents to take care of them as babies. Also, the fact that Adam’s first priority was to find a mate suggests he was created with a physically mature body.
In, we are given this account:
27 God created humanity in God’s own image,
in the divine image God created them,[ ]
male and female God created them.
28 God blessed them and said to them, “Be fertile and multiply; fill the earth and master it. Take charge of the fish of the sea, the birds in the sky, and everything crawling on the ground.” 29 Then God said, “I now give to you all the plants on the earth that yield seeds and all the trees whose fruit produces its seeds within it. These will be your food. 30 To all wildlife, to all the birds in the sky, and to everything crawling on the ground—to everything that breathes—I give all the green grasses for food.” And that’s what happened.
Again, this implies a physically and intellectually mature human pair with the capacity to procreate.