Primates have good vision, enlarged brains, and grasping hands and feet, and use their vision to guide reaching and grasping. Scientists have thought that these characteristics evolved together as early primates used their hands and eyes to grab insects and other small prey, or to handle and examine fruit and other foods.
Isbell suggests instead that primates developed good close-up eyesight to avoid a dangerous predator -- the snake.
"A snake is the only predator you really need to see close up. If it's a long way away it's not dangerous," Isbell said.
Neurological studies by others show that the structure of the brain's visual system does not actually fit with the idea that vision evolved along with reaching and grasping, Isbell said. But the visual system does seem to be well connected to the "fear module," brain structures involved in vigilance, fear and learning.
Fossils and DNA evidence show that snakes were likely the first serious predators of modern mammals, which evolved about 100 million years ago. Fossils of snakes with mouths big enough to eat those mammals appear at about the same time. Other animals that could have eaten our ancestors, such as big cats, and hawks and eagles, evolved much later.
Venomous snakes evolved about 60 million years ago, raising the stakes and forcing primates to get better at detecting them.
"There's an evolutionary arms race between the predators and prey. Primates get better at spotting and avoiding snakes, so the snakes get better at concealment, or more venomous, and the primates respond," Isbell said.
Some primate groups less threatened by snakes show fewer signs of evolutionary pressure to evolve better vision. For example, the lemurs of Madagascar do not have any venomous snakes in their environment, and in evolutionary terms "have stayed where they are," Isbell said. In South America, monkeys arrived millions of years before venomous snakes, and show less specialization in their visual system compared with Old World monkeys and apes, which all have good vision, including color.
Having evolved for one purpose, a good eye for color, detail and movement later became useful for other purposes, such as social interactions in groups.
Isbell is currently working on a book about primate origins, including her snake hypothesis.
Andy Fell | EurekAlert!
When fat cells change their colour
28.10.2016 | Albert-Ludwigs-Universität Freiburg im Breisgau
Aquaculture: Clear Water Thanks to Cork
28.10.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH
Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.
So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
28.10.2016 | Power and Electrical Engineering
28.10.2016 | Physics and Astronomy
28.10.2016 | Life Sciences