Here’s a really interesting article by the Observation Deck website entitled The Missing Link FAQs they explain the rise of the ‘Missing Link’ in popular science.
The ‘Missing Link’ is the idea that there is a stage in human evolution as yet undiscovered that bridges our ancestry with the rest of the animal kingdom.
It seems the term was coined in 1851 by Charles Lyell in relation to an undocumented rock formation stage which he dubbed ‘the missing link’. Later in an 1863 publication, he proposed that ‘human ancestry must be very far in the geological past, and that the linkage between humans and non-humans was, as of that time, missing.’
The term would later be used in 1868 by Ernst Haeckel who wrote a paper speaking about 22 distinct stages in man’s evolution and that the missing link was stage 21 as there were no fossils relating to this hypothetical period.
Since then the search for this missing link has continued throughout modern popular evolutionary biology and archaeology. The article has a very handy breakdown of evolution and the key fact to be remembered: that evolution is not a straight line.
Finally the article closes on the assertion that by definition almost all fossils discovered are an ‘evolutionary transitory fossil’ as evolution never stops.
And that evolution by it’s nature breaks out in small pockets of mutation that take hold or don’t, and this means a species does not evolve on one set evolutionary ladder but across different categories at different times.
Well, that makes sense. But what we take it to mean is that it may well be possible to an as yet undiscovered branch of human ancestor that evolved in it’s own separate path.