Our work on the generalizability of polygenic scores (PGS) from the @arbelharpak.bsky.social Lab is now officially out! We examine the accuracy of PGS predictions at the individual level. We make 3 observations that expose gaps in our understanding of PGS “portability.” rdcu.be/e0LAr (1/27)

The evolution of genetic drift over 50,000 generations https://www.biorxiv.org/content/10.64898/2026.01.25.701616v1

Balancing selection maintains some remarkable biological diversity, but detecting it from genomic data alone can be tricky. This may bias our view of its true prevalence. We investigated what makes balancing selection more or less detectable in genomic scans. + in thread & preprint!

General moment closure for the neutral two-locus Wright-Fisher dynamics https://www.biorxiv.org/content/10.64898/2026.01.16.700021v1

If you want to distract yourself while the world falls apart, this is a really cool paper from Amy that simultaneously solves many puzzling observations about malaria parasite genetics by positing the importance of multiple merges

Post-Doctoral Opportunity in Evolutionary and Conservation Genomics! If you are curious and passionate about ecology, evolution and the natural world come work with me in the Department of Biology at NYU! More details here! apply.interfolio.com/180051

Tracing the evolutionary histories of ultra-rare variants using variational dating of large ancestral recombination graphs https://www.biorxiv.org/content/10.64898/2026.01.07.698223v1

Global patterns of natural selection inferred using ancient DNA https://www.biorxiv.org/content/10.64898/2026.01.07.697984v1

Together with @ronghuizhu.bsky.social, we are thrilled to present our new perturb-seq study of 22M primary CD4+ T cells, across donors and timepoints – the result of a decade-long collaboration between the Marson @marsonlab.bsky.social and Pritchard @jkpritch.bsky.social labs 🧵 tinyurl.com/gwt2025

I'm just delighted to announce our new preprint on genome-scale perturb-seq in CD4+ T cells. We learned both general lessons about the power of perturb-seq, and specific lessons about T cell biology. Led by amazing postdocs Emma Dann and Ronghui Zhu, with my wonderful collaborator Alex Marson.

New preprint alert: we use sign errors as a test of how well TWAS works. Very worryingly we find that TWAS gets the sign wrong around 1/3 of the time (compared to 50% for pure guessing). You can read more about our analysis here, and what we think is going on 👇

How well does TWAS estimate a gene’s direction of effect on a trait? We think of this as an important stress-test for the accuracy of TWAS. In a new pre-print, we find that TWAS gets the sign wrong around 20-30% of the time! doi.org/10.64898/202... 1/n

Did you know there are 2 types of avocado varieties? A-types switch from female to male, B-types male to female, within a single day. This reciprocal sex alternation promotes cross-pollination and has a simple genetic basis. Read more in this recent preprint from the final chapter of my PhD thesis 🥑

Congrats @jeffgroh.bsky.social et al. Some avocado trees open female-phase flowers in the morning & then male in afternoon. Others show complementary pattern (m->f), to synchronize pollination of two types. Jeff show this to be a >45Mya polymorphism at a transcription factor across 100s of species.

How much better is an ancestral recombination graph (ARG) than a site frequency spectrum (SFS)? For recovering mutation rate history, we can answer fairly precisely because both ARG and SFS are linear transforms of mutation rate history. This blog post uses spectral analysis to clarify the picture.

Happy to highlight an essay I wrote together with @marcdemanuel.bsky.social, @natanaels.bsky.social and Anastasia Stolyarova, trying to think through what sets the mutation rate of a cell type in an animal species: www.biorxiv.org/content/10.6... 1/n

Grateful to share our paper on gene-specific selective sweeps in human gut microbiomes, now out in Nature! It has been a joy to work with @rwolff.bsky.social, whose insights and hard work made this possible. www.nature.com/articles/s41...

Preprint online right before the holidays! Excited to share the first piece of work from the Zhang Lab, led by my absolutely stellar postdoc Michelle Kim! In this work, we ask how admixture, selection and demography shape complex trait genetics and GWAS performance www.biorxiv.org/content/10.6...

Our latest preprint revisits the classic model of mutation-selection balance. Do human recessive genes fit Haldane's 100-year old model? This work is by the wonderful @jonj-udd.bsky.social, and co-mentored by @jeffspence.github.io www.biorxiv.org/content/10.6...

As a (to me very enjoyable) part of this paper, we worked out what mutation-selection balance looks like in finite populations with varying degrees of inbreeding.

GWAS has been an incredible discovery tool for human genetics: it regularly identifies *causal* links from 1000s of SNPs to any given trait. But mechanistic interpretation is usually difficult. Our latest work on causal models for this is out yesterday: www.nature.com/articles/s41... A short🧵:

With @szhan.bsky.social, @yulinzhang.bsky.social, Chao Zhang and Bingjie Chen, we wrote a Perspective about unifying the tree-based method across phylogenetics, population genetics and cell biology: arxiv.org/abs/2512.05499. Reposts are greatly appreciated!

BAPG 2025 was a blast. Looking forward to seeing folks in Davis in Spring 2026! bapg2025.github.io/bapg2025stan...

Our new ancient DNA paper has just been published! We present 28 new genomes from southern Africa - several of them high-coverage whole genomes. Exciting to be moving towards population-level representation of ancient southern African genetic diversity! www.nature.com/articles/s41...

Excited to share work from my postdoc with @docedge.bsky.social and collaborators Matt Pennell and @jgschraiber.bsky.social, newly out over the weekend: www.biorxiv.org/content/10.1... (1/6)

www.biorxiv.org/content/10.1... We finally submitted the earlier preprint to a journal after massive restructuring. We've expanded the REML section for those interested in the method. We clarify that ARG-LMM estimates mutational variance and not additive variance.

Interested in pleiotropy dissection but not sure where to start, which methods are useful, which studies offer illustrative examples, or how to robustly validate your results? Look no further 👀 rdcu.be/eSfAZ

We've got a really cool preprint out in collaboration with @lpachter.bsky.social's awesome student Cat Felce. Using biophysical models and RNA-seq data, we explore the mechanisms of selective constraint on mRNA abundance, finding constraint on decay rate www.biorxiv.org/content/10.1...

Work from my amazing undergrad @leyan-wang.bsky.social is just preprinted! TL;DR: If you worry that ARG methods might fail on unphased data due to phasing errors, you may not need to. Check it out & consider reposting to support a great young scientist!

Hitting refresh on biorxiv for a paper to appear... realized my first biorxiv preprint was more than 12 years ago, and on arXiv two years before that! Preprinting sure seemed strange at the time, but it's become my favorite part of the process! www.biorxiv.org/content/10.1... arxiv.org/abs/1208.0634

The last work of my PhD is finally out: www.pnas.org/doi/10.1073/...! This work is about accurately estimating branch length in the Ancestral Recombination Graph (ARG), which is achieved by a really simple framework with minimal assumptions. (1/n)

In an earlier project simulating quantitative traits/stabilizing selection in a human-Neanderthal model, I became a bit curious about some observed fitness dynamics that I wasn’t expecting. I’m not sure if this is all that interesting or relevant, but at least it’s short.

@hakha.bsky.social and I wrote a Research Briefing (with a lay summary + "behind the scenes") of our paper on how genes are prioritized by GWAS and rare variant burden tests. 🧬🧪 www.nature.com/articles/d41...

SAVE THE DATE: the yearly NY Population Genetics meeting will be back on March 9 2026, generously hosted by the @simonsfoundation.org. Details to follow. Please RT.

I am so excited to share new work on a TE insertion that regulates iridescence in swordtails, led by fantastic grad student @nadiahaghani.bsky.social and with help from many coauthors! In a time that has been so difficult to navigate, this & other projects have kept my spirits up: shorturl.at/NE65A

Super excited that the bulk of my PhD work is now preprinted! Here we used whole-community competition, or coalescence, experiments to quantify selection acting on genetically diverged strains within larger communities. (1/n) www.biorxiv.org/content/10.1...

An empirical approach to evaluating the prevalence of long-lived balancing selection in humans--and important limitations. Work by @hannahmm.bsky.social

How do GWAS and rare variant burden tests rank gene signals? In new work @nature.com with @hakha.bsky.social, @jkpritch.bsky.social, and our wonderful coauthors we find that the key factors are what we call Specificity, Length, and Luck! 🧬🧪🧵 www.nature.com/articles/s41...

Exciting new study led by @ekerdoncuff.bsky.social and @meaghanmarohn.bsky.social on the evolution of Lactase Persistence in South Asia. www.biorxiv.org/content/10.1...

This preprint shows that the huge recent progress of non-coding effect predictions is likely going to help tremendously in this area. A must read. www.biorxiv.org/content/10.1...

The Johri Lab has an open postdoc position. Please send me an email, if interested. Start date is flexible. Please do share! Thank you in advance.

How does life evolve to adapt to modern cities? Out now in Science, my PhD work with @lindymcbr.bsky.social uncovers the ancient origin of the “London Underground mosquito” – one of the most iconic examples of urban adaptation. 🧵(1/n) @science.org www.science.org/doi/10.1126/science.ady4515

Why do complex traits differ in their genetic architecture? In our new PLOS Biology paper, we will try to convince you that two simple scaling laws drive differences in the number, effect sizes and frequencies of causal variants affecting complex traits. Thread: journals.plos.org/plosbiology/...

One of the most exciting works of my career, years in the making. We used high-throughput precision genome editing to test the fitness effects of thousands of natural variants. Our findings challenge the long-held assumption that common variants are inconsequential. www.biorxiv.org/content/10.1...

For population genetics and evolutionary biology folks in the Bay Area: the next BAPG will be hosted by Stanford CEHG and the Petrov lab at Stanford on 12/6. Registration is free but required. The deadline for talk submission is Nov. 16. Hope to see you soon! Pls RT! docs.google.com/forms/d/e/1F...

If you need more exciting news about Denisovans, check out our paper on Denisovan ancestry in modern humans through time, out today in Current Biology: www.cell.com/current-biol...! #Denisovan #ancientDNA

We're excited to be recruiting an NIH funded postdoc to work in the Coop lab at UC Davis. We're specifically interested in candidates who are want to work at the intersection of human genetics, GWAS, and population genetics modeling. Please RT

New ad for an independent postdoc in mathematics/statistics/machine learning for Biology in my institute at RIKEN (not my lab), ranging from 3 to 7 years. Our institute is entirely English-run, and a good mix of expertise on maths/physics/stats/bio! www.riken.jp/en/careers/r...

PEQG website live! genetics-gsa.org/peqg-2026/

Our latest work is out in Nature today. In this paper, we introduce an improved version of NanoSeq, a duplex sequencing protocol with <5 errors per billion bp in single DNA molecules, and use it to study the somatic mutation landscape of oral epithelium in >1000 people www.nature.com/articles/s41...