18 thoughts on “More behavioral similarity between humans and apes

  1. Not to mention the Moro reflex, and, to my recent discovery, the Laser pointer reflex. My kids had never seen a laser pointer before. Their reaction was not unlike most felids (a startling and immediate attack of the strange red dot on the wall) and it entertained them for hours.

  2. Cute indeed. I suppose the four reflexes I’ve listed below are rooted in our arboreal past
    [I haven’t checked what the experts say on this though]

    ** Moro reflex: Baby is startled by a loud sound or movement

    Baby throws back her head, extends out the arms and legs, cries, then pulls the arms and legs back in
    Lasts about five to six months

    ** Tonic neck reflex: Turn baby’s head to one side

    The arm on that side stretches out and the opposite arm bends up at the elbow. This is often called the “fencing” position
    Lasts about six to seven months.

    ** Grasp reflex: Stroke the palm of baby’s hand

    Baby closes her fingers in a grasp
    Lasts only a couple of months and is stronger in premature babies

    ** Babinski reflex: Stroke the side of the foot

    Big toe bends back toward the top of the foot and the other toes fan out
    Lasts up to about 2 years of age

    Video of the Babinski [18 seconds]:

    1. Hmm… I can see why the grasp reflex would be useful for tree-dwelling infants; not so much the others. Surely the Moro reflex would end up with you falling? (Or is that a quick way of escaping danger? Then ball up as you fall to the ground…)


      1. “it involves 3 distinct components:

        spreading out the arms (abduction)
        unspreading the arms (adduction)
        crying (usually)

        “In human evolutionary history, the Moro reflex may have helped the infant cling to his mother while she carried him around all day. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother’s body.” [Wp]

    2. I was told a “just so” story years ago in three parts… I am speculating of course

      1] The auto-spreading of the arms was to snare any nearby branches as one fell from ones ‘perch’

      2] If the falling proto-human was unlucky with finding a branch to grasp then the reflex to tuck the arms kicked in

      3] Modern humans living on the ground are ill-equipped for falling. We tend to put our arms out as per the reflex, but there’s insufficient time to switch to the tuck mode before hitting the ground. Hence lots of broken wrists & hips. I’m not sure this counts as a Moro reflex since all ages do this however. The military has to train people to tuck & roll.

    3. If present in adults, Babinski’s reflex may be interpreted as a sign of neurological damage:

      I’ve always had the Babinski reflex and have been diagnosed with “hyperactive reflexes”.
      I asked my doctor about this a couple of years ago after a virus left me with extensive peripheral neuropathy. He said that my reflexes aren’t pathological, they are hereditary and not uncommon, since there is a wide range of reflexes in “normal” adult humans, from very active to quite sluggish. It’s only a change in an individual’s usual state that would indicate a problem.

      I have a cat with neurological problems due to a head injury as a kitten. When I pick him up, he automatically throws a paw around my arm, then draws all his paws in and stretches his head out as I hold him close. It’s cute and loving but very uncatlike…and makes me wonder how old some of these reflexes are, and where they originate in the brain. Some must go back to very early mammals.
      You can meet my Wonder Kitteh here:

      1. I was going to point out that the Babinski reflex is used as an indicator of neurological damage. Or (if I recall my decompression sickness assessment procedure correctly) to be more precise, the difference between Babinski reflex on either side is an indicator of damage in one or other leg’s nerves.

  3. The leg position is a “packaging” phenomenon. The fetus has to fit inside the womb and then exit the birth canal. After being “packaged” to do so, the baby’s legs and feet straighten out for its next trick: standing/walking. Interestingly, on the path between those two accomplishments, the legs first overcompensate, affecting the direction in which feet point, going from out-toed to in-toed, and then settle down to normal.

    1. That was my thought. Having had two kids, it’s pretty obvious they emerge from the womb all folded up to fit in that small space, and simply stay that way until their limbs need to unfurl for tasks like creeping, crawling, walking. It’s nothing to do with reflexes, vestigial or otherwise.

  4. It’s been a few years since I read WEIT, but would it be an atavism since it is a trait that seems to appear in all babies? I thought atavisms were for example, the whale legs that reappear rarely. Or humans born with tails. Or people who can wiggle their ears? Guessing I’m misremembering/misunderstanding something.

  5. I always treat medical students with respect. This is in the hope that one day, if we meet in a patient/doctor moment, they might at least warm the stethoscope first!

Leave a Reply