The development of the complex eye has often been cited as a reason evolution could not be possible. The eye is just too complicated. Nilsson and Pelger did a computer experiment. Starting with a few light sensitive cells, and changing just one element (avoiding Haldane’s problem–changing multiple factors at once) of the cells by 1/200 of a percent each generation (a year in this experiment), they were able to create a complex camera-type eye in 364,000 generations. In the real world, small fish were able to make the same changes in less than half a million years–a tiny fraction of the time in the experiment. Could a complex eye evolve? Easily and quickly.
Intelligent design? If you assume intelligent design, you assume that the actual design of the anatomy of animals is “intelligent”–efficient. The best way to do a certain function. A fish has two gills; each gill has its own artery and nerve. These continue lengthwise down the fish. So far, very efficient. Great design! In humans, one of these nerves has evolved into the laryngeal nerve, which controls the voice box and speech. This nerve begins in the head, goes down to the chest (just like a fish…) and then loops back to the voice box. In other words, the nerve travels several feet to end up a few inches from where it started. Efficient? No.
Or another example. Cephalopods (octopus, squid) have an eye similar to mammals, but all the nerves, arteries, and blood vessels are connected to the back of the retina. A mammal has a similar eye, but it developed differently: in the human eye, the nerves, arteries, and blood vessels are connected to the front (not the back) of the retina. They get in the way. So humans have a “blind spot.” Efficient? No.
Modern evolution? Sure–lactose tolerance. About 5-10,000 years ago N. Europeans began drinking milk. Humans have a gene that allows babies to drink milk, but after a couple years a gene shuts that ability off. The body loses the ability to digest milk easily. You get diarrhea and bloating. But those Europeans stuck to it, and their gene changed–now almost 100% of N. Europeans can drink milk with no problems. A genetic change–reacting to the evironment–in less than 10,000 years.
You could go on like this for volumes. Evolution is real and provable.