“The Flintstones” cartoon isn’t exactly vindicated, but a Field Museum biological anthropologist’s new theory suggests the earliest primates–ancestors of humans and apes–lived in the time of dinosaurs.
In a letter to be published Thursday in the British science journal Nature that is sure to spark controversy, a group of paleontologists and mathematicians led by Robert Martin, the Field Museum’s vice president for academic affairs, speculates primates first appeared 85 million years ago.
Because the oldest primate fossils ever found are about 55 million years old, most paleontologists have held that primates first evolved perhaps 60 million years ago, 5 million years after dinosaurs went extinct.
Martin’s theory challenges many long-held beliefs about where primitive primates first evolved and how they migrated through the world, eventually branching off into modern primates, including humans, apes, monkeys, lemurs, lorises and tarsiers.
“I suppose I am something of a heretic,” Martin said. “In 1988, I began to think primates must have originated much earlier than 55 million years ago.
“I couldn’t convince many of my fellow scientists, who like to stick to the evidence in the fossil record, so I had to bring in mathematicians to help me work this out.”
Martin and his colleagues invented a mathematical model they believe will be useful in more accurately determining the evolutionary timelines of all life-forms. It uses the earliest known fossils as a starting point to work backward to determine when their earliest ancestors evolved.
The mathematical model assumes animal species on average arise and thrive for about 2.5 million years before evolving into another species or becoming extinct. Factoring in the 235 modern primate species, 396 known fossil species and an estimated total of 8,000 to 9,000 primate species that ever lived, the researchers concluded primates in their most primitive form first appeared 85 million years ago.
The team’s calculations fall surprisingly close to those made by molecular biologists in recent DNA research on primate origins, which dates primates back to 80 million years ago.
Traditional paleontologists, however, like to stick to physical evidence provided by fossils.
“I am skeptical,” Marian Dagosto, a primate paleontologist who teaches anatomy at Northwestern University Medical School, said of Martin’s findings. In December she helped organize an international conference on primate origins at Northwestern and the Field Museum, at which Martin outlined his ideas.
“The traditional paleontological view is that primates probably first occur sometime after the Cretaceous extinction event [65 million years ago],” she said.
“To push it back this far [80 million to 85 million years ago] seems like a very long time to go back. There just is no fossil evidence that they do go back that far.”
There is no fossil evidence, Martin argues, because there are very few fossil-bearing rock formations from 200 million to 65 million years ago in the southern climates–in Africa, South America and India.
Because the earliest known primate fossils are found in northern climates, in Europe and the western United States, most paleontologists believe they first evolved there.
Martin said he thinks primates first evolved in the warm Southern Hemisphere, where much of early life evolved. He said they probably migrated to northern climates about 55 million years ago, when world temperatures suddenly rose by 18 degrees Fahrenheit.
“Our calculations indicate that we have fossil evidence for only about 5 percent of all extinct primates,” Martin said, “so it’s as if paleontologists have been trying to reconstruct a 1,000-piece jigsaw puzzle using just 50 pieces.”
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Informed by imaginative but anachronistic pop culture art forms in the 20th Century, such as “The Flintstones,” some people assume the earliest humans lived among dinosaurs.
Though humans didn’t evolve until nearly 60 million years after the last dinosaurs died, Martin’s theory at least has man’s earliest, tree-dwelling ancestor living in dinosaur times.
For Nature, Martin commissioned a drawing of how he believes the first primate might have looked.
It would have been small, weighing 1 to 2 pounds, sharing, he said, “all the primary characteristics of primates: large, forward-facing eyes, short snout, large brain, grasping hands and feet, [giving birth to a] small number of infants carried on mother’s fur.”