Skin below the head black?

I like to play Minecraft on 1.7.10 to test a few mods.

In this version, however, my skin is completely black except for the head…

In newer versions like 1.12.2 you can see the whole skin.

Does anyone know why?

I think it's because of the construct of the image where the skin is saved. In other words, if you download a skin it is strangely structured in the .png file.

I suspect that the 1.7 expects a different construct than the 1.12

The skin texture structures are always different. I think in version 1.7.10 you have to adapt your skin to this version. Just search for 1.12.2 and for 1.7.10 skins, then you know what I mean

But I made the skin myself