Homo erectus started with an average cranial size of 900 cc but went up to 1100 cc. They still have small brains, large eyebrow ridges, and projecting jaws:
From the neck down they are human:
Neanderthals:
These are probably the most like humans and are far more human-like than homo erectus. Some people argue that they are simply humans with expressed eye ridges. However take a look at an aboriginese.
Big eye ridge.
Take a look at their skulls:
Neanderthals have more radical eye ridges than even aborigines and just think how homo erectus would look. Neanderthals have 50% thinker bone than humans.
Neanderthals are also genertically different from us:
Fossil Hominids: mitochondrial DNA
Some may argue that we have not found a lot of fossils. We have found over 4,000 as of 1976 including 500 neanderthals, 150 homo erectus, and 150 homo afarensis.
CC030: Human fossils on a table
We see a general transition of brain sizes as we go back in time:
We even see a general increase in the humanness of the fossils over time:
Why are there these primitive humans before we see modern ones? What is up with the smooth transition.
We also have genetic evidence for evolution. Endogenous retroviruses can insert their DNA into humans and we can then pass on their genes to our children. In fact these sequences can be identified. Humans and chimps actually share retrovirus sequences and the same places showing our ancestry.
VWXYNot?: Endogenous retroviruses and the evidence for evolution
Endogenous retrovirus - Wikipedia, the free encyclopedia