# Key Points from #hplusroadmap IRC Discussion

• The "radiator theory" of brain evolution was challenged by evidence showing heat is not a major constraint on brain size, with research indicating brains could theoretically exceed the 5kg limit observed in nature, though temporal axonal delays remain constrained to ~0.03 seconds.

• Metabolic efficiency appears to shape neural information pathways, with research showing it costs 10^4 ATP molecules to transmit a bit at a chemical synapse and 10^6-10^7 ATP for graded signals or spike coding.

• Participants explored why general intelligence hasn't evolved more widely in animals, suggesting there must be significant constraints preventing hyperselection for intelligence despite its apparent advantages.

• An interesting hypothesis proposed that when hominids switched diets, nutritional deficiencies during development led to compensatory encephalization, with this extra brain capacity becoming available for higher cognitive functions once cooking was developed.

• Research was shared indicating that brain metabolism scales with allometric exponents that are multiples of 1/6 rather than 1/4, suggesting brain metabolism is more similar to aerobic than resting body metabolism.

• The "maternal energy hypothesis" was discussed as a potential limit on brain expansion, with cooking and fire usage potentially enabling humans to overcome primate brain size constraints.

• YCombinator announced $20,000 in free credit from Transcriptic (a remote robotic life science research lab) for their biotech companies, potentially doing for biotech what AWS did for web startups.