Zimmer

"The lineage that gave rise to dolphins, whales, and porpoises went through a transformation just as staggering as the one that brought vertebrates on land in the first place; about 50 million years ago a race of wolflife mammals began to adapt themselves to water. They lost their hind limbs altogether and turned their back on the place that had been their ancestors’ for over 250 million years."
Carl Zimmer "At the Water’s Edge

* * * * *

I once knew a fellow who told me that he had, when younger, spent a lot of time in the sea, surfing and swimming, and he began to notice something odd around the throat area. The man said he went to see a specialist who told him he was growing gills and it was suggested that the man stay away from sea water if he wanted to get rid of them.

Now you’re probably going to say – "Honey, this fellow was having a lend of you". Maybe, maybe not, but whether or not the story is true, the internet has been abuzz since 2004 with this news -

"The human parathyroid glands, which regulate the level of calcium in the blood, probably evolved from the gills of fish …"

"… A team from King's College London believe that they were internalised, rather than lost, when four-limbed, land-living animals evolved."

"… "… new research suggests that in fact, our gills are still sitting in our throats - disguised as our parathyroid glands."
http://news.bbc.co.uk

So though this information doesn’t exactly verify the story above, maybe it doesn’t sound quite so silly as on first mention.

From the same source as above,

‘Researcher Professor Anthony Graham said: "As the tetrapod parathyroid gland and the gills of fish both contribute to the regulation of extracellular calcium levels, it is reasonable to suggest that the parathyroid gland evolved from a transformation of the gills when animals made the transition from the aquatic to the terrestrial environment.’

As dolphins, whales and porpoises have done, is it possible that humans (I'm not saying all humans, but some humans) - over many many (many many many) generations - might morph back into under-water creatures?
----------------------------

Mermaid Picture: http://lair2000.net/mermaid39/mermaid39.html
and turn up the sound!