That was the Quora question.
David Pearce’s answer:
“Sentient beings shouldn’t hurt, harm, and kill each other. This isn’t an argument for mass genocide against cannibals or carnivores, but for dietary reform. Humans are prone to status quo bias. So let’s do a thought-experiment. Imagine we stumble across an advanced civilisation that has abolished predation, disease, famine, and all the horrors of primitive Darwinian life. The descendants of archaic lifeforms flourish unmolested in their wildlife parks – free living but not “wild”. Should we urge scrapping their regime of compassionate stewardship of the living world – and a return to asphyxiation, disembowelling and being eaten alive? Or is a happy biosphere best conserved intact?
“Back here on Earth, the exponential growth of computer power entails that every cubic metre of the planet will shortly be accessible to surveillance and micro-management. In consequence, which life-forms and states of consciousness exist in tomorrow’s wildlife parks will be up to us. Mass-produced in vitro meat, the CRISPR revolution in biotechnology, and fertility regulation via cross-species immunocontraception mean there is no need to re-enact the traditional Darwinian horror story indefinitely. On some fairly modest assumptions, fertility regulation is ethically preferable to Malthusian methods of population control in humans and nonhuman alike.
“Critics might claim that a genetically tweaked vegetarian lion isn’t “truly” a lion. But this is like saying non-Caucasians who lack the 1% to 3% Neanderthal DNA typical of Caucasians aren’t “truly” human. Or vice versa. In short, beware naive species essentialism.
“For now this debate is fanciful. Before humans can start systematically helping sentient beings, we must stop systematically harming them. Thankfully, the in vitro meat revolution promises a world where factory-farms and slaughterhouses have been outlawed. Before seriously contemplating high-tech Jainism, let’s shut the death factories.”