#19 — At the Intersections — August 29, 2026

A quasar's light signature alone can reveal its type, bypassing the need for a full spectrum. Tracking such patterns across distinct fields is the work of ComplexityPod. This week, our inquiries connect deep space, cellular biology, and human social function. We're starting with a classification problem in deep space—how to tell the difference between two types of quasars. Right, Type 1 and Type 2. Knowing the difference helps understand things like how active galaxies work. The standard method, spectroscopy, is accurate but it's also slow. And that's a problem of scale. Modern surveys are observing millions of quasars, so spectroscopy just can't keep up. The alternative is analyzing light curves from photometry, but the data is messy. It's irregularly sampled. You get readings at uneven times, which makes the data hard to work with. But a project with Pauline Barmby showed it's possible to use these light curves anyway. How did they get around the irregular sampling? They applied a technique called Slepian Wavelet Variance. It allows them to decompose the variance of these light curves across different timescales, essentially making sense of the messy data without needing a spectrum. And using that technique, they could classify the quasars based only on those variance curves. How well did it work? Very well. On a set of over 750 quasars, they had a 99 percent recovery rate for Type 1 and 87 percent for Type 2. And the few that were misclassified were outliers anyway—their light variability didn't match what their spectrum suggested. Now let's turn to the cellular level, to a phenomenon called microchimerism, which is the long-term presence of fetal cells in maternal tissue after pregnancy. It’s a common feature in mammals, but there’s a debate about its purpose. It was thought that maternal tissues might just accumulate these cells over successive pregnancies. But recent work shows that's not what happens. Fetal cells from a new pregnancy actively displace the older cells left over from previous ones. So the question is why. Why would this displacement evolve? Research with Geoff Wild used models to explore this, and the results point to an underlying conflict. Conflict between whom? The models suggest there are two opposing groups of cells in the mother's body. Cells from the current offspring want the mother to invest more resources into the current pregnancy. And the resident cells, from previous offspring, want the mother to conserve resources for future siblings. It's a tug-of-war over maternal investment. Exactly. So there’s a selective pressure for the incoming fetal cells to displace the resident ones, because that increases their faction's influence. This result supports what’s known as the Trojan Horse Hypothesis—the idea that fetal cells manipulate the mother for more resources. And it's a difficult outcome to square with the alternative, the Tolerance Hypothesis, which would predict that keeping a diverse mix of cells would be beneficial. Instead, the model suggests this loss of 'cellular memory' is just an expected outcome of evolutionary conflict between these cell lineages. Finally, we'll look at the connection between how thought is structured and a person's social ability, particularly in schizophrenia. The focus is on something called formal thought disorder, which is a determinant of social functioning. But past studies often lumped together its positive and negative dimensions. Even though those dimensions have different mechanisms. So a meta-analysis involving Lena Palaniyappan set out to look at their associations with social functioning separately. What did that analysis involve? It was substantial. For positive formal thought disorder, they combined data from 24 studies with over 4,000 participants. For the negative dimension, it was 7 studies with about 1,200 participants. And the findings showed that both dimensions were associated with poorer social functioning. But there was a difference in the strength of that connection. Right. The link was stronger for positive formal thought disorder—a robust pooled effect. The effect for the negative dimension was smaller and the evidence was considered more moderate. But that conclusion comes with a caveat, since there were far fewer studies on the negative side to begin with. True, so it's not considered a conclusive finding on its own. Still, the analysis suggests a path forward: since both dimensions are tied to poorer social outcomes, there is a need for interventions that directly target communication deficits, which positive formal thought disorder in particular seems to disrupt. That concludes this week's issue. We'll return with more research summaries next week. From ComplexityPod, thanks for listening.