David Reich – Why the Bronze Age was an inflection point in human evolution
David Reich is back.
He and collaborator Ali Akbari just published a paper that overturns a long-standing consensus about human evolution — that natural selection has been dormant in our species since the agricultural revolution.
By scaling ancient DNA sequencing and developing a new statistical method, they found that selection has actually sped up.
Selection went especially bonkers during the Bronze Age (around 3,000 years ago).
That’s when gene frequencies for everything from immune function to body fat to intelligence were most in flux.
Over the last 10,000 years, selection pushed the genetic predictor of cognitive performance up by roughly a full standard deviation — most of it between 4,000 and 2,000 years ago.
After we finished recording, David sketched out on a whiteboard his new heretical model about who the Neanderthals really were. Luckily, I took out my iPhone and managed to record it.
He thinks the standard story (that Neanderthals are some separate archaic lineage we interbred with a little) just doesn’t fit the evidence. Instead, he proposes that Neanderthals are essentially genetically-swamped modern humans.
A small population somewhere around the Caucasus invented Middle Stone Age technology roughly 300,000 years ago and expanded outward. The ones that moved into Europe interbred with local archaic humans, got genetically swamped, and became Neanderthals. The same expansion went into Africa, met much more diverged archaic Africans, and that mixture became us.
This means Neanderthals and modern humans share the same cultural ancestry — the only difference is which archaic humans they mixed with afterward.
David is a brilliant and rigorous scholar. It was a real delight to learn from him again.
Watch on YouTube; read the transcript.
Sponsors
* Cursor was super useful as I prepped for this episode. Whenever I had a question, I’d have Cursor kick off a few different models simultaneously and then compare their responses. I found that this led to better results than I could get out of any individual LLM. If you’ve only used Cursor for coding, you should try using it for research. Check it out at cursor.com/dwarkesh
* Jane Street uses an internal currency called “hive bucks” to allocate compute through a real-time auction – and anyone can change anyone else’s bids or even kill their jobs! Everyone just trusts each other to act in the firm’s best interest, which is what lets the system work in the first place. If this weird and high-trust culture sounds like your kind of thing, Jane Street’s hiring at janestreet.com/dwarkesh
* Crusoe’s ML infra team built fastokens, an open-source tokenizer that delivers a ~9x speedup over Hugging Face and up to 40% faster time-to-first token – on real production workloads! Crusoe achieved these results by parallelizing things and using some clever engineering to handle duplicates without cross-thread coordination. Learn more at crusoe.ai/dwarkesh
Timestamps
(00:00:00) – Ancient DNA suggests strong selection over last 10,000 years
(00:15:45) – Natural selection intensified during the Bronze Age
(00:35:02) – Why didn’t evolution max out intelligence?
(00:57:21) – Evolution is limited by time, not population size
(01:09:02) – Why no farming before the Ice Age?
(01:17:13) – The Neanderthal puzzle David can’t stop thinking about
(01:54:10) – The methodology behind this breakthrough
Get full access to Dwarkesh Podcast at www.dwarkesh.com/subscribe
David Reich — How one small tribe conquered the world 70,000 years ago
I had no idea how wild human history was before chatting with the geneticist of ancient DNA David Reich.
Human history has been again and again a story of one group figuring ‘something’ out, and then basically wiping everyone else out.
From the tribe of 1k-10k modern humans who killed off all the other human species 70,000 years ago; to the Yamnaya horse nomads 5,000 years ago who killed off 90+% of (then) Europeans and also destroyed the Indus Valley.
So much of what we thought we knew about human history is turning out to be wrong, from the ‘Out of Africa’ theory to the evolution of language, and this is all thanks to the research from David Reich’s lab.
Buy David Reich’s fascinating book, Who We Are How We Got Here.
Watch on YouTube. Listen on Apple Podcasts, Spotify, or any other podcast platform. Read the full transcript here.
Follow me on Twitter for updates on future episodes.
Sponsor
This episode is brought to you by Stripe, financial infrastructure for the internet. Millions of companies from Anthropic to Amazon use Stripe to accept payments, automate financial processes and grow their revenue.
If you’re interested in advertising on the podcast, check out this page.
Timestamps
(00:00:00) – Archaic and modern humans gene flow
(00:20:24) – How early modern humans dominated the world
(00:39:59) – How bubonic plague rewrote history
(00:50:03) – Was agriculture terrible for humans?
(00:59:28) – Yamnaya expansion and how populations collide
(01:15:39) – “Lost civilizations” and our Neanderthal ancestry
(01:31:32) – The DNA Challenge
(01:41:38) – David’s career: the genetic vocation
Get full access to Dwarkesh Podcast at www.dwarkesh.com/subscribe
a16z Podcast: The Scientific Revolution of Ancient DNA
with Jorge Conde (@jorgecondebio), David Reich, and Hanne Tidnam (@omnivorousread)
Trying to reconstruct the deep past of ancient humans out of present-day people has until now been like trying to reconstruct a bomb explosion in a room from bits of shrapnel, says David Reich, Professor of Genetics at Harvard Medical School and author of the new book, Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past. But technological advances and new tools available only in the last few years have suddenly revolutionized this field, opening up an entirely new window into the past as well as our present humanity.
This conversation, with a16z bio general parter Jorge Conde, and Hanne Tidnam, dives into this new scientific revolution of the study of the ancient genome. Beginning with the so-called "black hole" of Mitochondrial Eve to the most revelatory discoveries from new knowledge and scientific tools, this episode of the a16z Podcast delves into the ways archaic humans and ancient DNA tell us not just about our biology, but about ourselves.
image: Ben Casey, Wikimedia Commons
Stay Updated:
Find a16z on YouTube: YouTube
Find a16z on X
Find a16z on LinkedIn
Listen to the a16z Show on Spotify
Listen to the a16z Show on Apple Podcasts
Follow our host: https://twitter.com/eriktorenberg
Please note that the content here is for informational purposes only; should NOT be taken as legal, business, tax, or investment advice or be used to evaluate any investment or security; and is not directed at any investors or potential investors in any a16z fund. a16z and its affiliates may maintain investments in the companies discussed. For more details please see a16z.com/disclosures.
Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.