Was it smoking? Lead in automotive fuel? A childhood surviving a wolrd war? Scottish cooking?

The right image looks like it went through some filters on some smartphone...

Since the left image was on set, it is possible that he got makeup to make him look older.

One of these two people spent time in the sun to tan

Connery worked blue collar jobs as a teenager, and by the time he was 19 had been in the Royal Navy for a couple years. He then started training as a bodybuilder. He didn’t start acting until about then, and that was just for a little extra money.

The other fella is a child actor, starting his career when he was 11.

I think it's just genetics.

Here’s another still of Sean from Marnie (1964) tho, so I guess post is a bit misleading, since Sean looks just like his age at that moment, and photo in the post really feels like make-up to make him look older.

If anything, that’s Thomas Brodie-Sangster still looking 16.

VSauce made a really good video about this and there are definitely environmental factors making people today age slightly "better" than people in the past.

But yeah, this one is pretty much a nitpick of an older-than-30s looking guy against a baby-faced guy. Might as well put Michael Cera in there who’s almost 40 but still looks 16.

You think Connery is the odd one?

i think another big thing is that guys these days might actually be willing to use makeup, or at least something like a face cream.

Nah. He was just so sexy he always got rode hard and put away wet.

nah, Thomas is just built different