Polite Dissent

In the comments section of my recent post on Aquaman #19, Matt Rossi brings up an excellent point that I had missed entirely. It’s important enough to bear repeating:

How can Aquaman’s DNA be used to give people gills if he doesn’t have gills himself?

Speaking of gills, I just don’t think they’d work in people. A technologically based gill may be possible, but a biologically based gill doesn’t make sense.

I know sci-fi shows (remember SeaQuest DSV?) and comics show tiny slits in the neck for gills, but those wouldn’t be nearly large enough for human gills. Just like our lungs, surface area is very important in gills. Our lungs are designed for an oxygen rich environment (air contains 21% oxygen at sea level) and take up most of the ribcage. Water has much less oxygen (0-5% depending on temperature), so how large would gills need to be in humans?

Fish have different hemoglobin that grabs oxygen tighter than ours. This allows them to function at lower oxygen concentrations. Theoretically, human hemoglobin could be modified, but then a whole host of other modifications would need to be made down the line as well. For example, the myoglobin in muscle would also need to be modified or muscles would never get enough oxygen to function. Essentially every organ would need some genetic modification.

Finally, fish are cold-blooded and need much less energy (and oxygen) to survive. Notice that there are no warm-blooded animals with gills. All warm-blooded animals have lungs, even the aquatic ones.