Evolutionary steps

[Percy Mandible]

Is it taken for granted there are limitations or exceptions to the kind of statement following, or have I got hold of the wrong end of the stick? 
'Question - Are Homo erectus fossils found at the right time (i.e. after apes and before Homo sapiens) so as to establish them as legitimate ancestors to modern man?'
Doesn't the possibility (likelihood even?) of species or forms that represent earlier links in the evolutionary chain surviving alongside (chronologically, if not geographically) later forms or species make a nonsense of this? Or is geographical separation assumed in the comment?
But why should it be thought a 'less' evolved' species or form will inevitably give way to its 'fitter' successor? Don't creatures like Coelacanths and 'Hobbits' and amoeba belie this theory?
PS. I deliver pizzas for a living, so I'm not supposed to know much about this kind of thing. That doesn't preclude me from being interested, of course.
Percy   

[Mikey Brass]

'Question - Are Homo erectus fossils found at the right time (i.e. after apes and before Homo sapiens) so as to establish them as legitimate ancestors to modern man?'

Yes they are.

Doesn't the possibility (likelihood even?) of species or forms that represent earlier links in the evolutionary chain surviving alongside (chronologically, if not geographically) later forms or species make a nonsense of this? Or is geographical separation assumed in the comment?

There is nothing in biological evolution which means that the "mother species" has to become extinct.

Have you looked on http://www.bookfinder.com for a second-hand/new copy of either Richard Klein's "The Human Career" or Milford Wolpoff's "Paleoanthropology" ? They are standard texts and would provide you with a good, detailed overview background both in evolutionary theory and archaeology/palaeoanthropology.

[Percy Mandible]

Thanks Mikey.
But the two viewpoints are mutually exclusive (aren't they?). Common sense (plus and both yourself and myself) suggests that progenitor species can conceivably survive on alongside 'more evolved' brethren. There is no force to absolutely prohibit it that I ever heard of. Yet the quotation denies this, implying the evolutionary sequence must be reflected in the dating of remains. So that if were to be (have been) Sapiens remains found that clearly pre-date certain Erectus remains, then the presumed sequence is compromised - according to the quotation. To me, either the quotation is true, and wholly true, or it is dangerously flawed.
Finding 100,000 year old remains of Sapiens and 55,000-65,000 year old remains of Erectus does not necessarily negate the assumed evolutionary pattern. So finding remains that fall in the right dating order cannot prove the premise either, it would merely fail to disprove it - even if the remains are found in the same geographical area. 
That is the difficulty I have with the pronouncement.
We don't need to pursue this further - I think I have what I need. Thanks.
Percy the Pizza guy
     

[Mikey Brass]

implying the evolutionary sequence must be reflected in the dating of remains.

The hypothesised evolutionary sequence is derived from the avilable stratigraphic and radiometric evidence available. Should a key fossil or fossils be found to be older than previously thought, this necessitates a rethink. For example, in simple form, certain Homo sapiens fossil remains in the Levant were thought to post-date the Neanderthal remains but in actual fact they pre-date.

The parental form must always pre-date the daughter species. Should a fossil of a daughter species be claimed to pre-date the mother species then either the reconstructed sequence was flawed or the new reconstruction has serious issues which require addressing.

finding remains that fall in the right dating order cannot prove the premise either, it would merely fail to disprove it

Correct.

I also suggest reading some good online literature on evolutionary theory: http://www.talkorigins.org/origins/faqs-evolution.html