Da Vinci was wrong

One of the funniest things of working with data is taking something that is taken for granted as a universal truth and throwing it to the trash can. With Naiz Fit I entered a new realm that has proved to be unexpectedly stimulating, that is to study the human body.

We all remember some of those “rules of thumb” our art teachers or mothers told us … “The stature is eight times the head height”, “Your feet is the same length as your forearm”, etc… Are those fairy tales or do they have wisdom in them?

The Vitruvian Man and the 8-heads-to-stature canon

I remember my high school years studying some art (as part of the History course, not as an Art course). I love history but I did not understand why we had to study Da Vinci, as he did not have a historical role rather than a cultural role, but our teacher instructed us to admire Da Vinci and his work as virtuous and groundbreaking.

But he was wrong. And I was not told so.

One of the most famous drawings of Da Vinci is the Vitruvian Man. In this work, Da Vinci exposed his belief that the ideal human proportions were determined by the harmonious proportions that he believed governed the universe, in the sense of the roman Marcus Vitruvius Pollio, from whom the drawing takes it name.

The Vitruvian Man and it’s corresponding proportions. 8 Heads equals 1 Stature.

Back in the school, one of the assignments we had to study was this drawing, and I recall the teacher telling us that “the stature of the body is eight times the length of the head”. Suddenly all the class was getting out their rulers from their backpacks and measuring each other heads (with no method or rigor, of course) and after some roundings, consensus was promptly reached provided that there was some “minor” error: The proportion was correct. “The problem is that you are kids and the Vitruvian Man is an adult” stated the teacher, and with that excuse, that information was written in stone and remained in our minds.

Until some months ago, when I remembered that and as a joy, started tinkering with the Body Data we have at Naiz Fit.

A shot of the Naiz Corpus application we developed to keep track of body data and measures, displaying the data of our CEO.

First of all, let’s take a look at the stature data. We can find a somewhat normal distribution here. I took a sample of around 4.5K men from 18 to 65 years old from our database. The data sample is “spiky”, but it is more related with the fact that the data is continuous than (measured in milimeters) rather than error or dispersion.

The same happens with the Head Height. In this case as the measure of the head is around an order of magnitude lower than the stature, the sample is less spiky, but can be found that is of good statistical quality.

So, what happens when we cross those two variables?

Well, it turns out that there is no correlation. It is a big blob with a somewhat concentrated population but no signs of linear correlation between the two variables. I can tell you that I had some hope that the data correlated somehow, but that probably was the child in me begging for mercy, trying to convince the adult in me to not delete a memory of younger days.


I was a bad guy in this essay. I tried to fool you into the general notion that the real world and the idealized or platonic world are the same, and they aren’t. Da Vinci does not say anything about how bodies actually are, but how he thinks the virtuous body should be.

This “detail” is an error that permeates through all society. How many times around the day does preconceived things about how they should be get in the way of how they are? Why are we more comfortable with easy to remember -but wrong- rules rather than with what real data tells us?

Diversity, Ultrapersonalization, and even Long-Tail production are movements toward this, and that’s what I have been involved in for the last year and a half.

Here at Naiz we have a vision, that is to turn around the way the world is constructed regarding the interaction of our bodies with it. We think that we humans are building things for ourselves with a broken perception of our bodies, fueled by centuries of approximations and false premises about so many aspects of our body.

Some are fueled by religion, some by art, and other by the pursuit of perfection. But what the cruel data tells us is that all of them are crude approximations, which can be valid in the fields of art and culture, but completely wrong for designing things that we have to interact with.

This way, our vision is to help people build things thinking of the diversity of human bodies, so in the future, the world can adapt to our bodies and not our bodies to the world. We started with apparel and fashion, but we won’t end here.

Going back to the school, I remember another day with great detail. It was when, nearing the last quarter of the last course, our Physics teacher told us that “Newton was wrong”. This instantly caught our attention because it was like saying that everything we had learnt about gravity was false. After that, he said. “Well, not wrong, he only did an approximation” and we entered Einstein.

I can only dream of the day when future teachers say that Da Vinci was wrong and they explain the approximation with data.

But, stay vigilant! Data can also be used to confirm bias if used badly, and we have to be prepared to promptly identify when we are being fooled. I think that one of my favourite XCKD sketches regarding this is very conclusive:

Do you have any more proportions to debunk?

This is a call for all of you who have some of these truths about the human body. Please put them in the comments, pick them up and study them if interesting and follow up with new articles as this one!

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