The explanation is not actually correct, and misses a key mechanism in genetics.

A major observation about evolution is that it’s completely improbable that a new gene for something could appear in the genome by random mutation (this is the famous watchmaker argument, or the hurricane in a scrapyard making a 747). So how do new genes come about?

One mechanism is by gene duplication - this occurs by accident during DNA replication for example by an error in recombination. Basically a chunk of DNA that may include one or more genes ends up duplicated in an offspring so the offspring has 2 copies of one or more genes.

Because this duplicate gene creates a protein that already exists in the genetic plan, it probably won’t be too bad for the child, and so the offspring survive and may produce offspring of its own, ‘fixing’ this duplication in the population

Now mutation and selection can go to work and push one copy of the gene one way and the other in a different way, creating two different genes. Offspring carrying this new gene gain a selective benefit and so the gene becomes positively selected for and animals without the gene disappear from the gene pool.

This process occurs a lot, which is why we have families of hormones such as the steroids which handle both stress (eg adrenalin) and muscle growth (anabolic steroids) and immune system suppression (corticosteroids like prednisone) and sex steroids (estrogen, testosterone) - very different things but very similar chemically and genetically. It also explains why steroids in one family often have side effects such as weight gain, mood alteration and affecting sex drive.

Another example is the colour receptor in the retina of the eye. Fish, lizards and birds all have 4 colour receptors leading to fantastic colour definition from near infrared to low ultra-violet. Mammals lost two genes and in general can only see in 2 colours, red and blue.

Apes however duplicated the red receptor gene and the copy has gone through a few million years of mutation and selection that has drifted it up to detect green - humans see in red, green and blue. Our colour vision is possible only because of a gene duplication.

Or long word documents like theses.

Or a poorly-planned video editing background like myself.

It’s in the post: https://explainxkcd.com/3064/

Thanks, I missed that the link was in the post.

And it’s quite funny if you happen to have some programming background. If not, you tell me.

I am a software developer, and I just didn’t get the joke at all, even after reading the explanation…

The comic relates this to a common issue when editing documents or coding, where the author accidentally makes changes to two separately created versions of documents, when they meant to only edit one, which can result in changes to both (or all) resulting documents functionally essential parts of the completed project

Honestly not trying to be pedantic, joke just flew over my head I guess. 🤷‍♂️

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