When we read the natural history in the light of Darwin’s theory, we grant that all the variations inside the species were meant to improve the power of living. Moreover, since the exemplars of animals or plants are responsible for the improvement of their species, they seem to have a purposive nature which is unknown to them and hardly or even impossible to be determined through scientific observations.
When we explain such a purposive nature of animals and plants, we usually commit the error of describing it in terms of human affections: a natural purpose is understood as a human decision for becoming better. And there are decisions unknown to them.
Then, when we analyze the human exemplars according to the same theory, we recognize their purposive nature primarily on the level of the features of their species, and less in the individuals. Like in the case of other species, we admit there is almost impossible to view how the human individuals act for improve the existence of their species.
Moreover, by appealing again to the above mentioned error, it seems strange to assign something as human decisions to the nature of our body, as long as we commonly attribute them to human mind.
The improvement of a species means to provide to it a better place in the world. A better place for an individual is always one for its species. When we see the human beings that are always preoccupied with acquiring a better place in the world, it is the same care for their species. And all the humans do is well known to them. Thus, the individualistic activities inside of which the body is always involved tell more about the purposive nature of men than the features of their body.