Language families are usually drawn as diagrams. Heartwood takes the metaphor literally.

• Below the soil line are the reconstructed stages. No text of Proto-Indo-European survives; it is inferred backwards from everything above it, which is why it is drawn where you cannot see it.
• The trunk is the stretch where reconstruction is single, before the branches part.
• Each limb is one of the fourteen branches. Thickness and reach follow how many languages hang from it. The wood stays brown; a colored sapwood line and the leaves identify the branch.
• A branch with nothing living on it is drawn short and bare, low on the trunk: Anatolian, Tocharian, Phrygian, Thracian, Illyrian, Messapian.
• Each leaf is a language still spoken. A bare tip with a leaf on the ground below is one no longer spoken.

Heartwood is the dead core at the centre of a living trunk: wood that stopped growing and still carries the weight. Proto-Indo-European has not been spoken in five thousand years and holds up every form above it.

Height is not age. Each branch is given the same crown to reach into and divides it by how deeply it is subgrouped, because Romance is eleven levels of classification and Albanian is three, and letting one tower over the other would be a claim about time that the data does not make.

Growth angles and leaf scatter use a fixed seed, so the same data always grows the same tree and the downloaded image matches the screen. Classification from a curated Glottolog-derived tree.

Elsewhere: The Same Idea · The Missing N · Flat-Foot · Polite Company · Signs for Sounds · The Second Alphabet · Twenty-Two Letters · Brahmi's Daughters · The Same Word · Every Language Family