We already know that humans instinctively cry the second they enter the world. And now it turns out that marmosets monkeys (Callithrix jacchus) may have a similar reaction after they are birthed. Scientists have uncovered that these baby animals distinctly cry out loud to grab the attention of their caregivers. Here's what the research has shown...
A team at Princeton University wanted to better understand how "hard-wired" or natural traits become developed in babies. "People tend to ignore the fetal period," explained Darshana Narayanan, a behavioral neuroscientist who was a part of the research team. "They just think that it's like the baby's just vegetating and waiting to be born…. [But] that's where many things begin." Marmosets' development of vocalization is closely similar to how humans develop sound. This is why this specific animal was used for testing by using noninvasive ultrasound imaging on four different pregnant marmosets.
After investigating what was happening inside the womb of a mother marmoset, researchers revealed that the fetuses were actually able to move their mouths in a way that mimicked the special pattern of movement used to make the sound. At 95 days of pregnancy, the face becomes more visible, and what they saw was the fetus moving its mouth and head at the same tie. As time went on and the gestation moved along, the unborn monkey was able to move its head and facial features separately. The reason why no actual sound actually comes out is that it is so early on that the fetus hasn't even yet developed the production of sound. Moving their face in that motion helps prepare the baby to make the crying sounds once it's born. This research shows just how innate the feature in the monkey is.
The scientists noticed that the moments weren't random - but instead, they were moving exactly in the same way that a vocal marmoset would move its mouth to make the same sound. “The contact call is so unique that you really can’t mistake it for any of the other calls,” said Princeton biologist Asif Ghazanfar. But just to be sure they were accurate, the researchers tracked the fetal jaw movements frame-by-frame to determine their duration. They compared the amount of syllabus the fetus made to an already born money, and they were right! The development of sounds happens way earlier than we previously thought. “They have a long period of development — but in utero," explained Narayanan.