Not sure if all these fossils look all that different. On what basis are you determining that these fossils are all different from modern man?
Paleontologists, physical anthropologists and several other specialties deal with this topic. Both fossil man and human osteology were subjects I studied for my Ph.D. exams. I can assure you that your cursory look at those pictures differs drastically from what specialists do when they look at these skulls. Specialists have detailed knowledge of the anatomy and morphology involved, and will have looked at thousands of skulls and skull fragments of a wide range of species.
Believe it or not, experts in these fields actually know something!
If you took the fossil of a 19 year old man and compared it with the fossil of a 60 year old man what differences would you see?
I'll not detail the kinds of things you would expect, but between those two ages you give you would expect to see differences in dentition (3rd molar), suture closure, and age-related degeneration. These changes are all well known and can be found in standard text books.
If you were to extrapolate that difference to people who could potentially live till they were 800 years old what might you see?
Extrapolating the age-related changes we are familiar with, by age 800 you would have something approximating a jellyfish.
I am not suggesting that anyone could live 800 years but you never know what happened in the past right?
No that is not right. By studying ancient bones and fossils, archaeologists and paleontologists have a good idea of what happened in the past.
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.