Does the Darwinian theory require modification or replacement?
Absolutely. Every few years a scientist pops up negating bits of it. I preferthe original version seen in Genesis, which instigated the very premise of evolution. Consider:
1.That all life emerged as a dual-gender duality and then seperated as male/female - how else applies!
2. That the seed factor rules supreme and is not removable from the top preamble; Darwin does even mention it!
3. That the first factor distinquishing life form groupings is of terrain and habitat [water, air-borne, land, etc] - not hidden skeletal and dna.
4. Cross-speciation is introduced in Genesis, not by Darwin, and is conditional: a land based life form may follow its own land based kind. This is regardless if a fish creature adapted to wings.
5. That a species [kind] follows the program directive in its seed [inherited genes], not the environment. No evolution can occur without the seed factor. This negates that all life began from one life, to the only evidential one - the seed.