neutronbumblebee

The DESI Collaboration (https://en.wikipedia.org/wiki/Dark_Energy_Spectroscopic_Instrument) has released results from its first year of observations.

“The complex analysis used nearly 6 million galaxies and quasars and lets researchers see up to 11 billion years into the past. With just one year of data, DESI has made the most precise overall measurement of the growth of structure, surpassing previous efforts that took decades to make.” According to Dragan Huterer, professor at the University of Michigan and co-lead of DESI’s group.

https://web.ub.edu/en/web/actualitat/w/desi-force-gravity - New DESI results on the force of gravity

The analysis upholds general relativity but hints dark energy may vary over time. The result validates our leading model of the universe. It limits theories of modified gravity like MOND, which have been proposed as alternative ways to explain unexpected observations – including the accelerating expansion of our universe attributed to dark energy.

The standard model of cosmology summarizes our current best knowledge of the Universe. This is based on two well-established pillars of physics. Einstein's General Relativity, which regulates gravitation, and the standard model of particle physics, for all other basic interactions. However, it also relies on three key components — Inflation, Dark matter, and Dark energy that are critical for understanding a wide range of evidence, from the Cosmic Microwave Background to the Universe's Large Scale Structure.

The Dark Energy Spectroscopic Instrument (DESI) measures the effect of dark energy on the universe's expansion. Its completed survey will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3D map of the nearby universe.

“This is the first time that DESI has looked at the growth of cosmic structure. We’re showing a tremendous new ability to probe modified gravity and improve constraints on dark energy models. And it’s only the tip of the iceberg.”

Additional details on the implications for alternative gravity models in this paper - Ishak et al. (2024), Modified Gravity Constraints from the Full Shape Modeling of Clustering Measurements from DESI 2024 https://arxiv.org/abs/2411.12026

Links to the other original papers are here https://data.desi.lbl.gov/doc/papers/

Discoveries about a young ancestor's teeth may shed light on the upward trend in brain size over millennia.

Other explanations

Bipedalism developed long before bigger brains, and the use of tools was widespread in earlier hominid branches. As a result, these causes have been ruled out as the main driving force in brain evolution, despite being essential preconditions. https://efossils.org/book/bipedalism-vs-brain-size

Preteen teeth

The recent study of the 1.77 Million-year-old remains of an 11 to 12-year-old early homo from the Dmanisi site in Georgia is significant. https://phys.org/news/2024-11-fossil-teeth-childhood-prelude-evolution.html. This study of dental development throws some light on another human oddity, which is our very extended childhoods. The fossil's age places it close to the emergence of larger brains in our ancestors. A useful timeline is found here https://australian.museum/learn/science/human-evolution/larger-brains/

For context that's around this point in Human Evolution

Modern Human life history is distinguished by a prolonged childhood in which mental and somatic development rates diverge. This slow development is crucial for developing high cognitive abilities in our socially complex species.

A slowing childhood in a supportive family and cultural transmission

This individual experienced rapid growth in their first five years, faster than in apes. For example, their wisdom teeth fully emerged at 12 years of age compared to 17-24 today. This rapid growth was unexpected given the age of the fossil and its relationship to modern humans. However, the teeth did have a sequence of growth similar to modern humans. Marcia Ponce de León from the University of Zurich and co-author of the study commented "Milk teeth were used for longer than in the great apes and the children of this early Homo species were dependent on adult support for longer than those of the great apes". She suggests that "This could be the first evolutionary experiment of prolonged childhood".

It is believed that children's development slowed as cultural transmission increased, making the quantity of knowledge conveyed from old to young more crucial. This transmission would have allowed them to make greater use of available resources while developing more sophisticated behaviours, providing them with an evolutionary advantage.

The demands of large brains cause Humans to develop more slowly than our closest animal cousins. Energy directed toward the brain dominates the human body's metabolism early in life, which is possibly one other reason why humans develop at a rate more akin to a reptile than a mammal in early childhood. A five-year-old's brain is a real energy monster. It uses twice as much glucose as a fully grown adult. See https://www.sciencedaily.com/releases/2014/08/140825152558.htm

What does this explain?

However, just identifying some of the forces influencing the brain's evolution does not account for the emergence of more recent advances such as symbolic language. https://www.britannica.com/science/human-evolution/Language-culture-and-lifeways-in-the-Pleistocene Nonetheless, the brain's expansion was an essential precursor to the richness of human culture. Even in this early era of human evolution where children needed to mature rapidly, and life expectancy was low, adult care exerted a protective effect.

Additional Info

A variety of circumstances probably influenced brain development, including contributions from diverse hominid lineages with larger brains that were previously lumped into a single smaller smaller-brained species. Ian Tattersall provides a nuanced discussion of brain size and how it relates to humanities tangled origins in this 2023 article: Endocranial volumes and human evolution, https://pmc.ncbi.nlm.nih.gov/articles/PMC10517302/