The question was: How can a cuckoo reliably pass on the right egg color? After all, a female might not know what her own egg looks like.
Presumably, a female cuckoo will return to a nest of the type in which she was raised. For the egg color to really match, however, it needs to be encoded in the bird's genes. As far back as the 1930s, the hypothesis was formulated that the responsible genes reside somewhere on the maternal lineage.

The current analyses now confirm that the base color of the eggs of the European cuckoo is inherited almost exclusively via the female sex chromosome—the W chromosome—and mitochondria. The patterning, by contrast, depends to a greater extent on autosomal genes, which come from both parents. In the Oriental cuckoos studied, whose eggs were all whitish-green and differed only in their patterning, the researchers found no inheritance via the maternal lineage.
Inheritance via the W chromosome ensures that daughters always lay eggs with the same base color as their mothers. For new adaptations, however, this type of inheritance is suboptimal, as the possibilities of genetic variation are limited and more strongly dependent on random mutations than in the case of DNA inherited from both parents.
The researchers observed that a gene which 's possibly involved in egg coloration evidently 'migrated' from the autosomes [the non-sex chromosomes inherited from both parents] to the W chromosome.
Matrilineal inheritance shapes how genetic variation is spread across a species. When traits matter for both males and females, adapting to different hosts can quickly drive populations apart—and eventually create new species. In the cuckoo, by contrast, females can freely mate with any male without losing their adaptation to their host. The flow of genetic information across the rest of the genome is preserved.
And that is precisely what the researchers observed: The huge cuckoo population throughout Eurasia is almost genetically identical within DNA regions inherited from both parents.
But this evolutionary advantage does not protect the cuckoo from the dangers of the present. In many regions of Europe, populations are significantly declining, because their habitats are disappearing. "Without intact habitats, this fascinating system risks vanishing on our doorstep," caution the researchers.

Justin Merondun et al, Genomic architecture of egg mimicry and its consequences for speciation in parasitic cuckoos, Science (2025). DOI: 10.1126/science.adt9355

Part 2

AI gets ‘brain rot’ from social media
Artificial intelligence (AI) chatbots trained on ‘brain rot’ content — vapid social media posts that are the equivalent of mental junk food — are worse at generating accurate information. Researchers found that chatbots given a diet of popular and sensationalist Twitter/X posts skipped steps in their reasoning process (or didn’t use reasoning at all), spat out wrong answers and demonstrated ‘dark traits’ such as psychopathy and increased levels of narcissism.

Nature 
 arXiv preprint (not peer reviewed)

Chimpanzees rationally revise their beliefs

New evidence? No problem. Chimps can weigh conflicting clues, just like humans

Study is first to suggest our closest relatives think about their own thoughts

 Chimpanzees rationally revise their beliefs on the basis of evidence. 

In a series of play-based experiments at a Ugandan chimp sanctuary, researchers watched as the apes assessed the quality of the evidence before them, altered their behavior based on what they saw, and even revised their beliefs in light of new information. The results, published recently in Science, suggest chimpanzees can use the evidence in front of them to make smart decisions—and strengthen the case that these great apes think about their own thoughts, with awareness of what they do and don’t know.

https://www.science.org/doi/10.1126/science.adq5229