QUOTES: the ozone layer plays a key role in preserving the planet's biodiversity.

And now we may have a better idea of why that took so long -- more than 2 billion years -- to happen.

According to a new, Yale-led study, Earth's early atmosphere hosted a battle royale between iodine and oxygen -- effectively delaying the creation of a stable ozone layer that would shield complex life from much of the sun's ultraviolet radiation (UVR).

DAVID: another example of contingent processes which had to follow a certain course to give us eh Earth we have now. Chance or design?

Why would a designer who wanted diversity have designed a battle which delayed this diversity for 2 billion years?