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From Skeptical Rogue Bob Novella:

“Evolution is random. How could a random process result in such functional design?”

Evolution is not a random process. Natural selection, by definition (“selection”) involves a most decidedly non-random expansion of some traits in a population relative to others.

The key to understanding selection is that some individuals in a population at any given time will possess heritable traits (e.g., anatomical, physiological, behavioral) that provide an advantage over others in the population. They may resist heat or cold more effectively, have a more efficient digestive system for certain types of food, produce a more nourishing milk, have a natural immunity to some local disease, produce larger clutches of eggs, grow larger and more attractive antlers, communicate their needs and desires more effectively to other members of a social group . . . whatever. The result is, however, that those individuals with the advantage produce more surviving offspring during their lifetime than those at a disadvantage. So long as conditions persist to support those specific advantageous traits, then those traits will increase among members of the population, because it’s the individuals with those traits that are out-pacing the reproductive output of the individuals without those traits.

So where does this “random” notion come from? The ultimate source of variation in traits (the stuff on which selection acts) comes from genetic mutations. Changes in the nucleotide sequences in DNA may result in changes in genes and the proteins built from the genetic blueprint. Many mutations are deleterious, some have negligible influence on lifetime survivorship and reproductive success, and some may confer a selective advantage at a particular time and in a particular place. Those are the ones that get passed on to subsequent generations – the ones that ultimately transform the entire population. This is evolution.

There is design in nature. The process of selection is design. As Bob eloquently states, this design is bottom-up rather than top-down.

Killdeer on its nest. This creature is an example of exquisite design in anatomy, coloration, behavior, etc., all finely tuned to promote maximum lifetime reproductive success as a result of the process of natural selection.