Antelope eat grass and breed. If they eat faster than the grass can regrow, they starve and die, and their bodies become grass.
Death through starvation is unpleasant. Suppose they could agree to breed less, as to not expand beyond carrying capacity of the place they live in. They would lead a happier life.
Point being, some feedback-driven systems are good, and some are bad.
Why is the supposition that fewer lives is good controversial? What do we owe the unborn and non existent? Surely in any moral framework, if one could prove that additional organisms in an environment degrade the quality of life for all organisms, then it would be a moral decision (in principle) to reduce by attrition the number of new organisms? I am not arguing for population control as the mechanisms to achieve it are themselves morally dubious, but surely in principle we can agree that there is no moral imperative to grow a population, or alternatively that is not immoral to advocate for preventing population growth where it would reduce quality of life and lead to environmental degradation?
A moral framework is inherently subjective, so it should be no surprise that the rights of the unborn are considered more important in some than others.
Christianity arguably disagrees with you - see the tale of Onan. Buddhists likewise consider all life as sacred, in that an animal may previously/subsequently be a human soul. Lastly, many atheist progressives would argue that preservation of the human race is a moral imperative, and having more total humans rather than less ensures preservation in at least a simplistic mathematical sense.
> Christianity arguably disagrees with you - see the tale of Onan
"Be fruitful and multiply" is Genesis 1:28.
Onan is, per Jermone and canonical discussions, about spilling seed unnecessarily, but is more about not raping your sister-in-law and betraying dead family than it is about having many children. Nothing in there about the sacredness of babies or anything.
Onan's brother died and by tradition Onan entered into a Levirate marriage with his dead brother's wife, Tamar, to continue the brother's line. If Onan fathered a child by Tamar the child would inherit all of the dead brother's possessions and rights; if there were no sons Onan would inherit everything. So Onan pulls out, meaning he gets to bang the widow, and still gets to keep everything -- which is pretty sleazy.
God isn't really a fan of this, and punishes him accordingly.
> Lastly, many atheist progressives would argue that preservation of the human race is a moral imperative, and having more total humans rather than less ensures preservation in at least a simplistic mathematical sense.
It doesn't, because what I've essentially explained in my example. Too much population, and you collapse the environment, and human race suffers and then dies. I hope even smart atheist progressives would realize that meaningful ways to preserve human race are things like building a Mars colony, or ensuring the Earth's ecosystem does not collapse (such collapse would likely lead to great wars, possibly nuclear).
I would argue that a strictly rationalist or at least secular morality should be applied given the sheer religious or spiritual diversity of the global population.
And regarding your latter point,it is as you say simplistic - much like the proverbial bacterium on an agar plate, our growth imperative will destroy our future if we overrun the bounds of our environment. I think we will see the issue become more important as the consequences of overpopulation (with respect to resource consumption and carrying capacity) begin to bite.
Science cannot speak to general morality, as an abstract set of axiomatically good values, because it tends to tell us that those are completely arbitrary.
But science also teaches us that humans have a set of common, shared values, and while they may be arbitrary in general, they're not arbitrary to us. And they're shared, because humans are not isolated minds, each coming to existence ex nihilo, but in fact are connected through the process of reproduction. All of us have brain architecture we've inherited from a common ancestor.
This is how science can point us where to look for some practical morality.
Lions eat antelope; when they die their bodies become grass; the antelope eat the grass.
Suppose they all agreed not to do this.