My love is like a red red nose His tail is soft and tawny *

Mark Changizi has some interesting views about human trichromatic colour vision -- namely, that it evolved to facilitate social signalling, so that our ancestors could tell whether one another were blushing; and not (as is widely thought) so that they could detect ripe fruit against a background of foliage [of course one can see how the old incorrect theory came about, what with many historical descriptions of colour blindness involving complaints about "not being able to see fruit", while there are none that it caused "unawareness of everyone else's embarrassment" **].

No red-green vision

It is a theory and it is his. It predicts that other social mammals -- even ones that are not fruit-eaters like our primate ancestors and relatives -- should also have evolved trichromatic colour vision. Especially if, like us, they have a dearth of hair obscuring their skin. Sadly, elephants and dolphins and naked mole rats remain stubbornly dichromatic.

Mark Changizi is a person of interest to the Riddled research laboratory for his contributions to evolutionary psychology, which range from exploring the non-slip function of post-bathing human-fingertip prunyness, to explaining how the human brain co-evolved with Western classical music. Let us skip over his argument that evolution adapted the human nose to hold spectacles in exactly the right place in front of the eyes.

We had hoped that a science-blog scourge of ev-psych such as PZ Myers would already have had a whack at this current piñata of FAIL, but once again it turns out that if you want a job done properly you have to outsource it to a boiler-shop in Bangalore and then claim the credit. The main problem with Changizi's account is that human vision is not actually very good at recognising the signs of increased or decreased blood flow under the skin of the face; or the level of oxygenation of that blood.***

Seeing this as an opportunity rather than an obstacle, Changizi has a patent on rose-tinted "social spectacles", designed to filter the spectrum and enhance the visibility of veins against the skin. In other words, to provide the function that was provided by the evolution of colour vision. He is an exponent of the "making sow's-ears-ade" approach to difficulties.

That means people wearing shades don't need to miss seeing the blush of embarrassment or excitement on the face of a guy or girl on a first date. Similarly, a poker player hiding behind a pair of sunglasses could still spot a red flush creeping up the neck of an opponent ― a telltale sign that could clinch victory as surely as a five-card flush in the game.

But Riddled is not a place for summary rejection of novel ideas just because they are self-serving nonsense... we are all about the fairness and the natural justice and the payola from large corporations. To give Changizi's "subcutaneous vasculature" theory a fair suck of the saveloy we fired up the Riddled Evolvamat, to see if future species of humanity will develop increasingly transparent skin so that fluctuations in blood flow are even more visible to their peers.

The effects on Subject #1 (Greenish Hugh) were in line with expectations, except that his blood also turned transparent, rather missing the point.


Subject #2 sprouted an expressive tail and muscles along her muzzle, all the better to snarl at you with when you don't have the correct change for a pint of Wormwood Warmer.
The effect on Subject #3 was the appearance of an enticingly high forehead. Evidently its functionality is to support spare pairs of spectacles.

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* Responding -- four weeks late -- to a request from Substance McGravitas. Alternative title: The Color out of Face.

** There are numerous accounts from colour-blind doctors about the diagnostic difficulties caused by the deficiency. No-one has complained that "Can't tell if patient is embarrassed or choking".

*** Human wavelength discrimination is best at about 500 nm and 600 nm. Rather than a peak at 540-560 nm to match the peak of hemoglobin's light absorption, our wavelength sensitivity is relatively poor there.