Human babies cry significantly more than many other animal infants due to their unique evolutionary trajectory. Unlike many animals whose newborns are relatively self-sufficient at birth, human babies are exceptionally vulnerable and dependent. This prolonged period of helplessness necessitates more frequent crying to signal their needs.
The Evolutionary Explanation
The prolonged period of infancy in humans is linked to the significant development our brains undergo after birth. This rapid brain growth necessitates a longer period of dependence on caregivers for survival. As stated in a New York Times article, "Because the human brain is growing so quickly, it is harder for human babies to reach the point where they can keep their crying in check."1 This dependence translates directly into increased crying as a primary communication method for conveying hunger, discomfort, or the need for comfort and protection. Other animals whose young are more developed at birth require less frequent communication through crying.
A Discover Magazine article highlights this unique vulnerability: "This also fits in with the uniqueness of human babies, who are much more helpless than other baby animals that come out of the womb ready to walk and perform other basic functions. Human babies need more help, cry for assistance and comfort, and then (largely) grow out of crying as adults."2 This need for constant care and attention is a key driver behind the higher frequency of crying observed in human infants.
The Purpose of Crying
Crying is an innate survival mechanism across species, enabling young to solicit parental care. As explained in a New Scientist article, young humans emit cries to "obtain proximity to their caregivers, who then provide food, protection and reassurance."3 However, the intensity and frequency of this crying are amplified in human babies due to their prolonged dependency. This heightened crying ensures a higher probability of receiving the essential care necessary for survival and development. A study in Nature further supports this, stating that crying is an "innate survival mechanism...to maintain proximity to and obtain care"4
Key Differences
The following points summarize the key differences contributing to the disparity in crying between human and other animal babies:
- Brain Development: Humans undergo extensive brain development after birth, leading to a longer period of helplessness.
- Level of Independence: Animal newborns are often more self-sufficient at birth, reducing the need for frequent communication.
- Caregiver Reliance: Human babies are entirely dependent on caregivers for survival, leading to increased communication to fulfill their needs.
- Evolutionary Adaptation: The high frequency of crying in human babies is likely an evolutionary adaptation to ensure survival during this prolonged period of vulnerability.
[1] A Darwinian Look at a Wailing Baby - The New York Times. https://www.nytimes.com/2005/03/08/health/a-darwinian-look-at-a-wailing-baby.html
[2] Humans Are the Only Animals That Cry — And We Don't Know Why. Discover Magazine. https://www.discovermagazine.com/health/humans-are-the-only-animals-that-cry-and-we-dont-know-why
[3] Why are human infants so noisy compared with other young animals? New Scientist. https://www.newscientist.com/lastword/mg25333741-400-why-are-human-infants-so-noisy-compared-with-other-young-animals/
[4] Infant cries convey both stable and dynamic information about age and state. Nature. https://www.nature.com/articles/s44271-023-00022-z
