Why did people look older earlier in the past?

Whenever I stop and appreciate that most people my age in the 1960s would have owned a home with at least four kids, I feel a little embarrassed. Sure, they may have had access to a more robust dollar and a thriving post-war economy- arguably the greatest in human history- but it still makes me feel incredibly immature by comparison. I'm not the first to notice that people matured faster in the past. Even though I'll always love going to comic conventions, I understand that I'm preternaturally extending my lease on childhood a little too liberally.

However, their lifestyles and behaviors notwithstanding, people in the past physically looked older earlier. If you look at your parent's photo albums, you'll see exactly what I mean. In the video linked above, the YouTube channel Vsauce explains why it appears like people in the past looked more mature in their teens and 20s than people today.