I htink people under-estimate or more likely cannot conceive of the time-scales involved in evolution-they are BIG
from wiki
The basic timeline is a 4.6 billion year old Earth, with (very approximate) dates:
3.8 billion years of simple cells (prokaryotes),
3 billion years of photosynthesis,
2 billion years of complex cells (eukaryotes),
1 billion years of multicellular life,
600 million years of simple animals,
570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
550 million years of complex animals,
500 million years of fish and proto-amphibians,
475 million years of land plants,
400 million years of insects and seeds,
360 million years of amphibians,
300 million years of reptiles,
200 million years of mammals,
150 million years of birds,
130 million years of flowers,
65 million years since the non-avian dinosaurs died out,
2.5 million years since the appearance of the genus Homo,
200,000 years since humans started looking like they do today,
25,000 years since Neanderthals died out.
evolution isn't just survival of the fittest,
there has been random mutation of DNA over a massive amount of time leading to new genes/proteins/life-forms. Survival of the fittest is the process by which the variants that are more or less suitable are rejected, or expand to fill a particular niche to which they are more suited.
I am not religious any more, I have no belief in a creator, but as a scientist I am awestruck by the minutiae of our bodies and cells profoundly grateful to get a chance to study just a teeny-weeny corner of development in detail. The complexity of what is going on inside us all the time is mind-boggling, but I find it a lot easier to believe that it came into being incredibly gradually over time than it was all created instantly by someone waving their magic wand (or godly equivalent).