The palmar grasp reflex is neither useless nor evidence of an ape past
The palmar grasp reflex occurs when the infant’s fingers reflexively flex around an object placed in its palm such as a caregiver’s finger. The response is the result of a spinal reflex controlled by the higher brain centres.1 This reflex, a universal trait of all healthy human infants, develops as early as in a 16-week-old fetus. As documented during routine ultrasound examination, the fetus begins to grasp the umbilical cord in the mother’s womb as early as 25 weeks.2 It persists until the development of rudimentary fine motor skills between age two to six months.
After the baby’s fingers spontaneously curl around the object, they can hold on so tightly that the baby is able to support its body weight thereby. Stroking the back of the baby’s hand usually will release its grip. When hanging by its hands from a horizontal rod, the baby’s grasp reflex can hold its weight for about 10 seconds. In contrast, monkey infants are able to hang by one hand for more than half an hour. This reflex is essential for monkey infants to cling to the mother’s body fur to nurse and travel from one location to another with the mother.
The palmar grasp reflex is listed as one of the seven leading examples of vestigial organs by the Encyclopedia Britannica. 3 Some evolutionists list it as a vestigial behaviour rather than an organ, but the ability is genetic and requires both the proper anatomy and physiology. The vestigial claim is even featured in several YouTube videos. In one example, the narrator calls the palmar grasp reflex “the most adorable vestigial behaviour”.4 The video shows a baby supporting its own weight, attributing its strong grip to its “inner monkey” (3:48).
Rogers, in an article about vestigial organs, admits: “Despite its diminished strength and loss in early infancy, some researchers think that the grasp reflex may retain important functions in humans.”3 Rogers has a point; even from an evolutionary perspective, if it had no important functions in humans, why would such a complex system have been maintained by selection?
The palmar reflex involves the premotor cortex, supplementary cortex, the brain cingulate motor cortex, and the spinal relay centre located in the cervical spinal cord. These systems are all involved in controlling the grasp reflex through the spinal interneurons. In addition, also involved are the afferent nerve fibres, including the ulnar and median sensory nerves that supply the palmar surface, and the motor nerves that supply the hand’s flexors and adductors.5 But there are more reasons than this complexity to support Rogers’ statement.
The social bonding function
The mechanism of grasping, in other primates as well as in humans, appears to be significant in the social bonding needed for healthy emotional development. In the 1950s and 60s, psychological research was dominated by psychoanalysts and behaviourists, who espoused the view that babies became attached to their mothers largely because they provided food. Henry Harlow argued that this perspective overlooked the critical importance of contact comfort (touch/feel, including the infant clutching its mother), companionship, and love in promoting healthy development. Harlow took infant monkeys from their biological mothers and placed them with inanimate surrogate mothers. One surrogate ‘mother’ was constructed from wire and wood, and the second ‘mother’ was covered in foam rubber and soft terry cloth. The monkeys assigned to the foam rubber and soft terry cloth mother fared far better developmentally.6
Those with the wire and wood mother, though given a good diet, manifested very disturbed behaviour, sometimes staring blankly for hours, circling their cages, and engaging in self-mutilation. If these infants were re-introduced to their peer group, many stayed separate, some even refusing to eat.
Modern researchers on human development stress the need for various forms of physical interaction for the healthy development of human infants as well. The palmar reflex is increasingly regarded as important in helping to develop the bond between mother, father (and others), and the baby.7 A common behaviour of adult persons is to grab hold of an infant’s hand to experience the grasping reflex. Other forms of contact are important, and the palmar reflex is only one means of contact, but a very important one in the infant’s early socialization.8
Clinical implications of the grasp reflex
The numerous functions of the grasping reflex include its ability to stimulate the development of normal neurons and neural pathways that are foundational for later voluntary movements. Problems in this grasping reflex stage can cause developmental problems. Numerous studies document that for this reason, the reflex is a very important diagnostic tool.9 In fact, the “plantar grasp reflex is of great clinical significance”, especially in terms of the early detection of disease.2
The palmar reflex is significantly more common in the infants of primates that carry their young by having them hang onto their mother’s fur. This fact is used to support the theory that the grasping reflex evolved in species where the young can hold onto their mother’s fur. This observation incorrectly indicates to evolutionists that the grasping reflex is vestigial in humans and other non-fur-carrying primates.10
This reflex is believed by evolutionists to have been essential in our distant monkey ancestors; enabling infants to cling onto their mother’s fur while travelling and nursing.11 One problem with this theory is that the young can be carried by different methods besides fur grasping, as is common in many primates. These other modes include oral holds, as is common in cats, or even riding on their mother’s back.
Nonetheless, this reflex in humans is considered a major proof that humans evolved from monkey ancestors that lived an arboreal existence. When our ancestors lost their fur body-covering, according to Darwinists, the infants no longer required a powerful grasp but the genes and anatomy continued to display the grasp reflex. As it is not required in humans, infants typically begin to lose the reflex around the age of three months.11 One of many problems with this fur-grabbing theory is that the grasping reflex is needed to properly develop higher levels of conscious hand and arm behaviour in many primate species. In a field study of this behaviour, Peckre observed that, of the 21 species of strepsirrhines studied, “fur-carrying species exhibited significantly more frequent manual grasping of food items”.10 This finding supports the fact that manual dexterity which exists for fur grasping also logically facilitates manual food-grasping development as well as grasping of other objects.
The prevalence of the Darwinist explanation for the human grasping reflex causes it to be commonly labelled as a ‘primitive’ trait. In a study of 47 premature infants, the grasping reflex, which the researchers labelled a ‘primitive reflex’, was present in all 47.12 The title of the article used the term evolution when what was studied was normal development, not biological evolution. Although several theories of its evolution exist, as Peckre admits: “The origin and evolution of manual grasping remain poorly understood.”13
The palmar grasp reflex is not vestigial, but has important functions including particularly as part of the developmental process leading up to the use of the hand for complex life in our human society. It is part of the design of the human body and involves many brain, nerve, muscle, tendon, and ligament systems. It also serves the important role of facilitating more effective bonding of the infant with its mother and other adults.
References and notes
- Anekar, A. and Bordoni, B., Palmar grasp reflex, StatPearls, ncbi.nlm.nih.gov/books/NBK553133/, 9 September 2020. Return to text.
- Futagi, Y., Toribe, Y., and Suzuki, Y., The grasp reflex and moro reflex in infants: hierarchy of primitive reflex responses, International J. of Pediatrics 2012(12):191562 ǀ doi.org/10.1155/2012/191562. Return to text.
- Rogers, K., 7 Vestigial features of the human body, Britannica, britannica.com/list/7-vestigial-features-of-the-human-body, 2012. Return to text.
- youtube.com/watch?v=rFxu7NEoKC8. See also youtube.com/watch?v=3upCBO27Wqw (2:31), and youtube.com/watch?v=NAxCQwuUPHM (2:59) Return to text.
- Mireia, R.Q., Palmar grasp reflex: check the evolution in your own body, allyouneedisbiology.wordpress.com/tag/palmar-grasp-reflex/, 18 April 2016. Return to text.
- Harlow, H.F., Dodsworth, R.O., and Harlow, M.K., Total social isolation in monkeys, PNAS 54(1):90–97, June 1965. Return to text.
- Rhona, L. and Kristen, M., (reviewer) All about your baby’s grasping reflex, Healthline Parenthood, healthline.com/health/baby/grasp-reflex, 24 November 2020. Return to text.
- Mason, W.A., Early social deprivation in the nonhuman primates: implications for human behavior; in: Glass, D.C. (Ed.), Environmental Influences, Rockefeller University and Russell Sage Foundation, New York, pp. 70–101, 1968. Return to text.
- de Moraes, M.V.M., Dionisio, J., Tan, U., and Tudella, E., Palmar grasp reflex in human newborns, Pediatrics and Therapeutics 7(1), January 2017 | doi:10.4172/2161-0665.1000309. Return to text.
- Peckre, L. et al., Holding-on: co-evolution between infant carrying and grasping behavior in strepsirrhines, Scientific Reports 6:37729, 2016. Return to text.
- Vestigial organs, Science Oxford, scienceoxford.com/vestigial-organs/, 17 July 2015. Return to text.
- Allen, M. and Capute, A.J., The evolution of primitive reflexes in extremely premature infants, Pediatric Research 20(12):1284–1289, 1986. Return to text.
- Peckre, L. et al., ref. 10, p. 1. Return to text.