here'th thumbthing interethting

You might recall, if you follow me on Twitter/X, and why in the name of God would you, that I have occasionally - as a twisted means of expressing my love for, and pride in, my kids, though in a typically British oblique and emotionally-repressed way - mentioned some of their fascinating genetic traits, all thankfully on the quirky and endearing side of the dividing line that separates them from the more extreme tentacly Lovecraftian horrors that must be DESTROYED WITH FIRE.

A couple of examples are below:

fascinatingly-named genetic conditions that I exhibit which I have passed on to my eldest daughter: Darwin's tubercle (unilateral), Morton's toe (bilateral, as I think it always is). also, Shatner's bassoon, etc. #genetics

— Dave Thomas (@electrichalibut) January 13, 2020

the internet is great. I have one of these, as do my father and my eldest daughter. wife and other two kids don't have it. FREAKS! https://t.co/sh0F1C1dwL

— Dave Thomas (@electrichalibut) June 25, 2019

Another example follows: I'm not sure that we've applied a greater level of scrutiny to the boy in terms of his development after his early arrival and spending the first 91 days of his life in a series of gradually-larger plastic boxes with bleepy machines attached in hospital, but I suppose it's plausible that we might have. Anyway, one thing I've always noticed about Huwie is what I perceive to be his freakishly enormous thumbs. I have always taken this as an indication of future tallness as an adult once the rest of his anatomy catches up with his thumbs - as an aside, although he is currently slightly below average height for his age, the canonical example of teeny prematurity not being a bar to tallness and sporting prowess as an adult is recently-retired cricketer Stuart Broad, born at 28 weeks (Huwie was 27) but eventually a strapping 6 feet 5 inches.

However, it turns out that this may have been en error of perspective - I don't mean that I was accidentally holding the boy's thumbs really close, more that my expectations for appropriate child thumb size will have been influenced by my two daughters. And why not, you might say, except that Nia, who is generally curious about all things and now has a phone with access to the internet, ran into the kitchen the other day excitedly shouting "Dad, I've got toe thumbs!". Sorry, love, you've got what? "Alys has got them too!" Hang on, what?

Well, it turns out that "toe thumbs" are actually a thing, that particular phrase being one of several common colloquial descriptions of a genetic trait more properly called brachydactyly type D. This is the most common form of brachydactyly, supposedly affecting around 2-3% of the population. To illustrate, here is a parade of thumbs:

So you can see that Huwie's thumbnails are almost circular or perhaps even elliptical, with the major axis oriented vertically, whereas Nia's are elliptical(ish) with the major axis oriented horizontally and Alys' thumbnails barely exist at all. We're not fully comparing apples with apples here because Alys (like me) is an inveterate nail-biter while Nia and Huwie are not. Nonetheless there is a stark contrast between Huwie's thumbs, which give a general impression of tapering elegantly, and the girls' thumbs which are squared-off and stubby. No suggestion of any other genetic consequences of having weird thumbs, thankfully, and the only practical consequence is that neither of the girls will be able to play the guitar in the style of Richie Havens. 

So if it's an inheritable genetic trait, Dave, you'll be saying, what do your thumbs look like?

My desk isn't broken, by the way; I had to stitch two images together (badly) owing to a need to have a hand to hold the camera with. It's hard to be objective about something that, after 50+ years of looking at them, implicitly defines my mental image of what a "normal" thumb looks like, but I'd say I occupy a centre ground between Huwie and the girls. My ellipses are definitely horizontal but there's a bit more nail (even allowing for their bitten state) than, say, Alys has. 

Just for completeness, Hazel's are below. She has pretty regular vertical ellipses, so I have to conclude that it's me who is the carrier of the genetic freakery here.