Dolphins are smarter than most creatures, but why is that? Now, there's genetic evidence to prove that like humans, a good portion of its genetic makeup is devoted to the development of its nervous system.

This discovery shows that intelligence is an important characteristic for dolphins, more so than most other mammals. Descended from mesonychids, an extinct order of carnivorous hoofed animals that resembled wolves, their transformation into fish like aquatic mammals was the result of some extreme modifications. Because of all of these factors, dolphins are a particularly interesting species to study from both an evolutionary and genetic perspective.

The study of the bottlenose dolphin genome was conducted by a team of researchers at Baylor College of Medicine in Houston and it was part of a study of some other 29 mammalian genomes. Scientists wanted to know how different dolphins were from a genetic perspective.

They looked up over 10,000 genes with counterparts in the genomes of nine other mammals, including humans, elephants, dogs, horses and cows. They discovered that 228 gene sequences were different in dolphins compared to other mammals, and 10% of those changes were related to the dolphin's nervous system.

Scientists also uncovered a group of genes that was much related to a similar set found in humans, one that's connected to brain disorders - for example Alzheimer's and schizophrenia. This could imply that dolphins suffer from these conditions as well.

Genetic differences were also seen in dolphin lung development –- a morphological change that was most certainly beneficial for an aquatic mammal. The team also found a gene related to hair growth, and it's known that dolphins have small hairs when they're calves - hinting an indication that the species were derived from a hairy terrestrial animal.

What's more interesting is how scientists found a genetic similarity that's common in humans and elephants, namely a decline in the rate of change exhibited by their DNA sequences over time.

The comparative analysis of mammalian genomes is available at Nature.