Well, they got the ‘when” kind of right.
Unfortunately, the PBS team had no idea how, who, or why bats took flight.
The following is my summary comment
buried deeper on the PBS YouTube page with each passing hour and day:
“With phylogenetic analysis based on traits we know the ancestors of bats back to jawless fish. Currently Zhangheotherium, a basal pangolin, and Chriacus are proximal outgroups to bats. (see link below). DNA fails too often in deep time experiments (e.g. Laurasiatheria: camels, whales, etc.)
“The best way to understand the genesis of bat flght is to compare it to the colugo, which leaps from its perch and glides for distance using membranes stretched between long limbs. These membranes were coopted from an extended marsupium, a place to keep newborns safe in these very basal placentals not far from their marsupial ancestors. Colugos, like many primitive placentals, also hang upside down, but with four very long limbs and small fingers.
“By contrast bats are inverted bipeds with membranes stretched between elongate fingers and short hind limbs. They don’t fly like birds and pterosaurs do. Instead they push pulses of air down with their huge parachute-like wings and huge pectoral muscles. When pre-bats hung inverted from low branches, they were able to survey the leaf litter below, ready to pounce on insects and worms rustling in the leaves on the ground. The distance could have started at 10cm, then extended to a meter, then 10 meters. So that is where hyper-acute hearing first developed.
“Instead of leaping from tree to tree, pre-bats dropped straight down onto their prey. To slow their fall, they flapped their large parachute-type hands. These became larger over time. Embryo bats with big hands recapitulate the evolution of bats. Leaf litter provided a soft landing for the tiny parachuting pre-bats, but over time flapping before crashing slowly turned into hovering for accuracy inches above the leaf litter before pouncing. Some bats still do this today. Over still more time, improved hovering became flight.
“After flight, returning to their inverted roost was so much safer, due to no more tree trunk climbing.”
More details, images and links here: https://pterosaurheresies.wordpress.com/2018/06/18/the-origin-and-evolution-of-bats-part-4-distance-vs-accuracy/
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