In a landmark episode of the Guardian's Science Weekly podcast released on 4 December 2025, host Ian Sample delved into a revolutionary new framework for understanding the human brain and a medical breakthrough that could redefine ageing.
The Five Eras of the Human Brain
Leading the discussion was Professor David Linden of Johns Hopkins University School of Medicine, author of the new book 'Unique Brain: The New Science of Individuality'. He proposed a compelling model that divides the brain's evolutionary journey into five distinct epochs.
This model begins with the 'Era of Cellular Innovation', dating back over 600 million years, when the first nerve cells and simple neural networks emerged. Next came the 'Era of Connection', where brains developed more complex wiring. The third stage, the 'Era of Expansion', saw a significant increase in brain size.
The fourth and crucial 'Era of Reorganisation' involved the development of new brain areas and sophisticated circuits. Finally, we are now living in the 'Era of Embodiment', where the brain's interaction with the body, environment, and culture shapes its unique function in every individual.
A Pioneering Vaccine to Combat Dementia
The podcast then shifted to a major clinical development with profound implications for public health. Ian Sample interviewed Dr. John M. Reed, President of Global Research and Development at the pharmaceutical company Servier.
They discussed the promising results from a phase 3 clinical trial for a new vaccine targeting dementia. The treatment, known as ACI-35.030, is designed to train the immune system to attack a specific, misfolded form of the tau protein—a key culprit in the progression of Alzheimer's disease.
The 18-month trial involved 1,114 participants across 26 countries, all in the early symptomatic stages of Alzheimer's. The findings, presented at the 2025 Clinical Trials on Alzheimer's Disease conference, were striking. Patients receiving the vaccine showed a statistically significant slowing of clinical decline compared to those on a placebo.
Perhaps most notably, the vaccine demonstrated a stronger effect in individuals carrying the APOE4 gene variant, a known genetic risk factor for Alzheimer's. This suggests a targeted efficacy that could protect those most vulnerable. The treatment also exhibited a favourable safety profile, with most side-effects being mild or moderate.
Unexpected Altruism in the Insect World
Adding a fascinating behavioural angle to the episode, the podcast featured the work of researcher Erik Frank from the University of Lausanne. His study, published in the journal Current Biology, observed remarkable altruism in Matabele ants (Megaponera analis) in Ivory Coast.
These ants, which hunt termites, display extraordinary care for wounded comrades. Individual ants were observed consistently returning to rescue specific injured nest-mates after battles, carrying them back to the nest to recover. This behaviour indicates a complex level of social bonding and recognition previously thought to be rare in insects.
The episode concluded by weaving these threads together, highlighting how understanding our brain's deep past, protecting its future from disease, and studying complex social behaviour in other species all contribute to a richer picture of intelligence, health, and survival.
