I am a humanities person rather than a sciences person, and I therefore claim no particular expertise in science; my interest in the subject is more in the area of the relationship between science, theology and philosophy than in science per se. Having said that, my understanding is that one of the greatest challenges posed to the theory of evolution as proposed by Darwin and his modern interpreters comes from the fields of genetics and information theory. Essentially - again, as I understand it - discoveries and advances in these fields since the 1950s suggest that the mutations which Darwin claimed were the driving force of the "natural selection" process have since been discovered to represent a decrease rather than an increase in the information encoded in the subject genome. In lay terms, a genome is a blueprint, if you like, for an organism; a mutation does not add new information to the blueprint, enabling a more complex organism to "evolve", rather it scrambles information from the original blueprint. According to this approach, any physical adaptation of a species to a new environment therefore represents a re-arrangement or tweaking of information already existant in the blueprint. Needless to say, this presents a major stumbling block to evolutionary theory - unless it is overcome, there is less reason to invoke the "blind watchmaker" of evolutionary theory, to borrow Richard Dawkins' phrase, and more compelling evidence for an intelligent designer of life.
In the following video, Richard Dawkins, a man rarely at a loss for words, appears stumped when asked to give an example of a mutation that has resulted in increased information being added to a genome. The video was part of a film produced c. 1997, but was apparently not included in the film as is because the question was actually asked during a break in the interview by the camera person, who was not miked - though the question is still audible - and it has only come to light recently. Claims of a hoax through editing appear to have been substantially answered by the camera operator in question, who has provided a timeline of the whole interview showing where cuts were made. The only cut in the video shown below occurs at Dawkins' own request for "time to think", after which he offers an answer which has absolutely nothing to do with the question, what is known to humanities types like me as the informal fallacy of ignoratio elenchi , or irrelevant conclusion. Interesting.