But is this a new thing? Or unique to humans? I'd think if humans in a stable, wealthy community today have fewer children than those in a high-risk community t

But is this a new thing? Or unique to humans? I'd think if humans in a stable, wealthy community today have fewer children than those in a high-risk community then perhaps early humans who were living in a comfortable environment also had fewer children than those who were fighting against predators and famine. We should be able to find other species populations that exhibit the same relationship between infant mortality and frequency of birth.