Lead scientist on the National Science Foundation (NSF)-funded project is Lori Marino of Emory University in Atlanta; colleagues Daniel McShea from Duke University in North Carolina and Mark Uhen from the Cranbrook Institute of Science in Bloomfield, Michigan, are co-investigators on the study.
Dolphin brains are four to five times larger than would be expected for their body size when compared to another animal of similar size. In humans, the measure is seven times larger. "Essentially, the brains of primates and cetaceans arrived at the same cognitive space while evolving along different paths," Marino says. "What the data say to me is that we, as humans, are not that special. Although we are highly encephalized [have large brains], it's not by much compared with cetaceans."
The scientists investigated the fossil record of the toothed whales (which includes dolphins, porpoises, belugas and narwhals) from the order Cetacea, suborder Odontoceti. Many modern toothed whale species (Odontocetes) have extremely large brains significantly larger than expected for their body sizes and second only to those of modern humans.
"A description of the pattern of encephalization [brain size] in toothed whales has enormous potential to yield new insights into Odontocete evolution: whether there are shared features with hominoid brain evolution, and more generally how large brains evolve," Marino says.
To investigate how the large brains of Odontocetes changed over time, Marino and her colleagues quantified and averaged estimates of brain and body size for fossil cetacean
Contact: Cheryl Dybas
National Science Foundation