Baboons Branch Off: Old World Monkeys

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Author note.

Explore voice = Exploratory style. Very punchy. Personal, and lively using “me,” “you,” “us,” and “I” freely.

I want you to feel me right there with you. We use “I” and “me” and “us” without apology. If the Explain voice is a bridge, the Explore voice is the hike we take across it. It is lively, reflective, and sometimes a bit raw. It is the sound of a shared exploration where I lead you by the hand, but we both discover the view at the same time.

This is where I get to think out loud. Not with definitions, we aren’t just looking at the facts; we are looking at how they feel and what they mean for our lives. I’m talking to you about what I’ve found and what I’m still figuring out. It is engaging because it is real, and it is reflective because it is honest.

The goal is real advice and enjoyable reading. I want to land on something you can actually use. It’s about being direct, being punchy, and making sure that by the time we reach the end of the page, we’ve both found something worth keeping.

And now the piece.

Baboons Branch Off: Old World Monkeys

27 Million Years Ago (+/- 2 million)

Large neocortex, Coalition politics emerge

The last common ancestor with humans and old-world monkeys lived around 29 million years ago.

Around 25 to 29 million years ago, Old World monkeys, including species like baboons and macaques, branched off from the common ancestor shared with apes. Unlike their ape cousins, Old World monkeys retained their tails and adapted to a wider range of habitats, from forests to savannas. Baboons, known for their ground-dwelling behavior, exhibit strong social structures and advanced communication. However, they lack the opposable thumbs and tool use that evolved in the ape lineage. This branching marked a key evolutionary moment, setting the stage for the development of the tailless apes, including gibbons and later great apes.

Primary Timeline…

Here's the key idea. Our last tails! The last common ancestor with humans and old-world monkeys lived around 29 million years ago.

Finally, the core takeaway. By 27 million years ago, our ancestors had opposable thumbs and could sit upright, but they still had tails and mostly moved on all fours. From this common ancestral population, evolution unfolded in two related ways. Anagenesis describes the slow, continuous changes within a single lineage: subtle shifts in anatomy and behavior accumulating generation by generation. Cladogenesis, by contrast, occurs when a population gradually splits into separate lineages that then evolve independently. In this case, one branch would eventually give rise to Old World monkeys, including baboons, while another continued down the path that would later lead to apes and, much later, humans.

That History Story,

was first published on TST 2 years ago.

The flashcard inspired by it is this.

Front: What evolutionary process occurs when one species splits into two or more distinct species?

Back: Cladogenesis (evolution involving lineage splitting into two species)

All this is part of the broader TST project.

When a source is corrected or expanded, it can be updated once at the tidbit level and reflected everywhere it appears.

By keeping editions identifiable and research reusable, the project remains coherent even as its thinking evolves.

The end!