Humans look so different from their closest relatives

[Calpalned]

3) How is Heidelbergensis the ancestor of both

modern humans and neanderthals? As mentioned in the first question,

neanderthals look quite similar to heidelbergensis, so I understand

the connection. However, compared to Heidelbergensis, modern human

skulls look quite alien. That is to say, no brow ridge, the presence

of a chin and perhaps most striking is the round shape of the cranium

(whereas all other hominids had elongated oval shaped craniums).

 

[Simon Bridge]

I don't look much like my dad, does that mean we're not related?

 

[Calpalned]

I don't look much like my dad, does that mean we're not related?

Parents and children are generally within the same species (I use generally because certain animals have interbred and created things like wolphins). For humans, they are all within the same species. My question is that skulls that are labeled as modern "belonging to homo sapiens sapiens" are unusual compared to those of their closest relatives outside of their species (aka the hominids). All of the hominids, be it neanderthal, homo erectus, homo heidelbergensis, austropithecus etc all had brow ridges and lacked chins. All other species of homo, in addition, had craniums (part protecting brain) shaped quite differently from that of humans. It is more of an enlongated oval shape. As stated in this article, we are the only hominids with chins http://www.smithsonianmag.com/science-nature/why-do-humans-have-chins-15140492/?no-ist Why is it that modern humans look so different from other hominids, while the diverse species of hominids look quite similar to each other?

 

[Simon Bridge]

If there were no striking differences, then they would be the same species rather than close relatives.
If you want to know how homonid skulls get characterized, look into cladistics. I gave you a link.