Why are Neanderthals considered a separate species from humans?

The fossil record is certainly not perfect.

Not even very complete, realistically, almost non-existent.

>Neanderthals went extinct around 40,000 years ago.

Are there any more extreme opportunities for survivorship bias?

1. Race is a social construct, not a biological one (https://www.sulc.edu/assets/sulc/officeequityinclusiontitlei...)

2. The fossil record shows that Neanderthals evolved in Europe and Western Asia approximately 400,000 years ago, while anatomically modern humans emerged in Africa around 300,000 years ago. Neanderthals went extinct around 40,000 years ago.