Why? Because that would make humans’ existence “less special.”
From New Scientist
Today, the CMB’s temperature is just a few degrees above absolute zero. But Loeb calculates that about 15 million years after the big bang, the radiation would have been warm enough to make the whole universe one large habitable zone. This life-friendly epoch would have lasted a few million years, enough time for microbes to emerge but not complex life, says Loeb.
…
As wacky as the idea of such ancient life seems, Loeb thinks it is worth exploring if it puts a dent in the anthropic principle. This hotly debated idea in cosmology says that the fundamental constants in the universe are tuned in just the right way for us to be around to observe them.
As usual, the moralizing kicks in:
“The anthropic argument gives us an excuse for not seeking a more fundamental understanding,” says Loeb. That makes the notion of “big bang life” appealing. The denser regions of matter needed for it to arise would have also required a cosmological constant a million times larger than ours. That would mean life existed in our universe even at a time when the value of the cosmological constant would not have favoured humans, making our existence less special.
It is possible that life evolved during Loeb’s habitable epoch, agrees Alexander Vilenkin at Tufts University in Medford, Massachusetts. However, he reckons the odds of it happening are very low, and that most life in our universe should instead be suited to today’s conditions, so from a statistical view the anthropic principle lives on.
The fact that the statistics point in the direction of the anthropic principle does not count in the long run as evidence in the principle’s favor, of course. The need for humans to be “less special” stands in for evidence. As a result,
… , evidence is now superfluous. Methodological naturalism produced the Copernican Principle, which is an axiom. It axiomatically accounts for our universe’s apparent fine tuning by postulating — without the need for evidence — an infinity of flops. And cosmologists’ acceptance makes the multiverse orthodoxy.
And compared to speculating that infinity of universes into existence, speculating a few strange exoplanets and microbes at the Big Bang is small change.
Note: Only fifteen million years? Instead of more like fifteen billion? Look, would it help if we brought it down to fifteen thousand? That is, would this guy embrace an atheistic form of young Earth creationism if he could thereby dispense with fine-tuning? One has to wonder.