history - When did people living for 900 years start to look old?

In the early days of the world, the standard age of living was well into the hundreds, with many people living until they were 800 or 900. Being that people lived so long, when did they start to "look old"?

For example, would someone 100 years old look like a modern 100, or perhaps a modern 20?

Answer

Bava Metzia 87a:

Until Abraham there was no old age; whoever wished to speak to Abraham would speak to Isaac, and the reverse. Thereupon he prayed, and old age came into existence, as it is written, And Abraham was old and well-stricken in age.

So during the age when people lived 200+ years, they showed no signs of age.