The question "Which brain is bigger?" requires clarification as it depends on the species being compared. There isn't a single definitive answer.
Comparing Brain Sizes Across Species
The largest brains belong to sperm whales, weighing approximately 8 kg (18 lb). This significantly surpasses the brain size of elephants (just over 5 kg or 11 lb), bottlenose dolphins (1.5 to 1.7 kg or 3.3 to 3.7 lb), and humans (around 1.3 to 1.5 kg or 2.9 to 3.3 lb). [Source: Reference information provided]
- Sperm Whale: ~8 kg (18 lb)
- Elephant: ~5 kg (11 lb)
- Bottlenose Dolphin: 1.5-1.7 kg (3.3-3.7 lb)
- Human: 1.3-1.5 kg (2.9-3.3 lb)
It's crucial to note that brain size alone doesn't equate to intelligence. While humans possess relatively large brains compared to body size, other species have larger brains overall.
Comparing Human Brain Sizes: Male vs. Female
Research indicates that, on average, male brains are 10% to 15% larger than female brains, even when adjusting for body height differences. [Source: Multiple references provided, including Are Sex Differences in Human Brain Structure Associated With Sex Differences in Cognition?] However, this size difference doesn't correlate with intelligence. [Source: Battle of the Brain: Men Vs. Women [Infographic]]
Changes in Human Brain Size Over Time
Interestingly, studies suggest human brains were larger approximately 3,000 years ago than they are today. [Source: Why human brains were bigger 3,000 years ago] Recent research also shows human brains are currently getting larger, potentially impacting dementia risk. [Source: Human brains are getting larger. That may be good news for ...]
Conclusion
Therefore, the "biggest brain" varies depending on the context. Sperm whales possess the largest brains overall. Within the human population, males tend to have larger brains than females, but this difference doesn't indicate superior intelligence. Brain size has also fluctuated throughout human history.
