The University of Texas at Austin suggest after examining the skull of the oldest known penguin fossil.
The findings were published in the Journal of Anatomy in February.
"What this seems to indicate is that becoming larger, losing flight and becoming a wing-propelled diver does not necessarily change the [brain] anatomy quickly," said James Proffitt, a graduate student at the university's Jackson School of Geosciences who led the research.
"The way the modern penguin brain looks doesn't show up until millions and millions of years later."
The findings were published in the Journal of Anatomy in February.
"What this seems to indicate is that becoming larger, losing flight and becoming a wing-propelled diver does not necessarily change the [brain] anatomy quickly," said James Proffitt, a graduate student at the university's Jackson School of Geosciences who led the research.
"The way the modern penguin brain looks doesn't show up until millions and millions of years later."