Many people including scientists have thought that there must be a missing link for Darwins theory of evolution to be through. Well, within the next few paragraphs here you'll see why that's a completely ridiculous notion to consider that there "must" be a missing link.
While the theory of evolution may be true, the biggest flaw is that it doesn't consider environmental forces directly changing us. Darwins theory suggests that we basically change ourselves through an ability-or inability to survive with "random" mutations. In a completely controlled environment however, there are likely no random mutations, but that's another story altogether.
There is a ridiculous number of environmental substances which can alter us before and after birth. Radiation being the prime example, which is spread throughout the universe and caused by a number of things. There are even "toxins" which may alter DNA, such as certain mold toxins and other environmental toxins.
With some DNA altering substances being spread on massive scales, it seems to be blindsiding the issue by denying the possibility, or even the high likelihood that environmental substances may be playing a role in the process of evolution. While there would be few bad examples of mass-scale DNA altering substances having their effect (because things effected badly would be no more), there may be many living examples of DNA altering substances gone right, such as chemical changes through courses of diet which would greatly add to reasons for why different people and animals vary so much from place to place when they have the same basic environmental challenges- It's not definitely because people less equipped die off and only leave the people most equipped, it's also likely that foods of the area, toxins, and other environmental factors could literally be changing the people from the inside out.