This would make them less

[keannu]

Does this "would" refer to "a habitual action" or "future in the past"?

gp52) Recently people have found a smiling face on the surface of Mars...The phenomenon that allows people to see the image of a person or a thing in another object is known as "pareidolia"....So why does this happen? Some scientists believe that pareidolia is a trait that we humans developed through evolution to help us survive. A million years ago, babies who were unable to recognize their parents' faces smiled back less, and were less likely to be loved by their parents. This would make them less likely to survive. So, it would seem that the ability to identify the human face is hard-wired in our brains...

[emsr2d2]

It's simply stating a scientific belief that a million years ago, some babies could not recognise their parents' faces and as a result smiled less and were loved less. That made them less likely to survive.
The writer has chosen to use "This would make them ..." instead of "This made them ...". You would have to ask him/her why.
The same can be said for the closing sentence. There is no reason to use "It would seem that ..." instead of "It seems that ..."

It suggests a tiny amount of questionability in the statement perhaps. "It seems that ..." sounds quite certain. "It would seem ..." sounds perhaps a little more hesitant.

[keannu]

I thought it's "it used to make them less likely to survive" as a habitual incident, and this is one of the possiblities or the writer was not careful. Thank you, anyway!!!

[JMurray]

Some scientists believe that pareidolia is a trait that we humans developed through evolution to help us survive. A million years ago, babies who were unable to recognize their parents' faces smiled back less, and were less likely to be loved by their parents. This would make them less likely to survive. So, it would seem that the ability to identify the human face is hard-wired in our brains...

Perhaps the "would" is a result of the conditional mood suggested by the previous two sentences. The passage might be summarized as: "Some scientists believe that babies who were unable to recognize their parents' faces, were less likely to be loved by their parents. (If so,) this would make them less likely to survive".

not a teacher

[keannu]

If it refers to a conditional mood, why isn't a past one? Like (If so), this would have made them less likely to survive. It jumped from the past to the present, which may be possible, but I don't know. As emsr said, only the writer may know. Sometimes I feel it's a waste of time concentrating too much on a vague sentence.

[emsr2d2]

Sometimes I feel as if it's a waste of time concentrating too much on a vague sentence.

I couldn't agree more.