I believe that in developed nations, the nutrients that are most lacking in a child's diet are the; calcium, iron and zinc. Zinc is needed for the activity of more than 100 different enzymes in the body and plays a role in the immune function. It aids in the maintenance of healthy immune function in kids and may reduce the frequency of mild upper respiratory tract infections. Calcium keeps the bones healthy and teeth thus supporting the skeletal structure and function. Iron is an important component of hemoglobin.
The steps get More specific
Yes, they ate the only mammals which could fly because flying squirrels, possums or etc. could only glide for a short distance and time, unlike bats. There are no reptiles who could fly, but there are reptiles who could glide which I think is completely different. But they said that Pterosaur existed which they believed it is a flying reptile dinosaur. Just look it up. :)
The earliest forms would be plants and other life like that, and current day would be mostly humans and animals and a lot of plants are disappearing