> A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.

If that's the case, it was almost certainly because of the atmospheric oxygen.

Almost all of the chemical reactions that used to happen before it do not happen anymore on the wild.

> A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.

Probably for the same reason we don't see relay or valve based digital computers anymore. They were outcompeted to extinction by their more sophisticated descendants.

> A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.

The general thinking is that DNA evolved from RNA, which has certainly not dissappeared.

As to pre RNA chemistry, there is a good chance that the relevent chemicals still exist and are well studied. The issue is more that we have not worked out the specific proccess that led to the development of abundant RNA.