Frameshift

“Well,” said Klimus, after taking another sip of wine, “you know I’m spending a lot of time at the Institute of Human Origins.” The IHO was also in Berkeley; its director was Donald Johanson, discoverer of the famous Australopithecus afarensis known as Lucy. “I’m hoping to make progress with Hapless Hannah’s DNA in resolving the out-of-Africa debate.”

“Great film,” said Molly lightly, really not wishing to see the conversation devolve into shoptalk. “Meryl Streep was excellent.”

Klimus raised an eyebrow. “I know Pierre knows about Hannah, Molly, but do you?”

She shook her head. He told her about his breakthrough with extracting intact DNA from the Israeli Neanderthal bones, then paused to fortify himself with another sip of wine. Pierre got up to open a second bottle.

“Well,” said Klimus, “there are two competing models for the origin of modern humans. One is called the out-of-Africa hypothesis; the other is the multiregional hypothesis. They both agree that Homo erectus started spreading out from Africa into Eurasia as much as one-point-eight million years ago — Java man, Peking man, Heidelberg man, those are all specimens of erectus.

“But the out-of-Africa hypothesis says that modern man, Homo sapiens — which may or may not include Neanderthals as a subgroup — evolved in east Africa, but didn’t expand out of there until a second migration from Africa just one or two hundred thousand years ago. The out-of-Africa proponents say that when this second wave caught up with various erectus groups in Asia and Europe, they defeated them, leaving Homo sapiens as the only extant species of humanity.”

He paused long enough to let Pierre pour him another glass of wine.

“The multiregional hypothesis is quite different. It says all those erectus populations went on evolving, and they each gave rise independently to modern man. That would explain why Homo sapiens seems to appear in the fossil record pretty much simultaneously across all of Eurasia.”

“But surely,” said Molly, intrigued despite herself, “if you have isolated populations, you’d end up with different species evolving in each area — like on the Galapagos Islands.” She rose to start clearing the dishes.

Klimus handed her his dinner plate. “The multiregionalists contend that there was a lot of inbreeding among the various populations, allowing them to evolve in tandem.”

“Inbreeding from France all the way to Indonesia?” said Molly, disappearing into the kitchen for a moment. “And I thought my sister got around.”

Pierre laughed, but when Molly returned she was shaking her head. “I don’t know,” she said. “This multiregional stuff seems more like an exercise in political correctness than good science — an attempt to avoid Felix Sousa’s which-race-came-first question and say, ‘Hey, we all evolved together at once.’ ”

Klimus nodded. “Ordinarily, I should agree with you, but there are excellent sequences of skulls going all the way from Homo erectus through Neanderthal man and into fully modern humans in Java and China. It does look like independent evolution toward Homo sapiens went on at least in those locations, and possibly elsewhere, too.”

“But that’s evolutionarily absurd,” said Molly. “Surely the classical model of evolution says that, through mutation, one individual in a population spontaneously gains a survival advantage, and then his or her offspring, because of that advantage, outcompete everyone else, eventually creating a new species.”

Pierre got up to help Molly serve dessert — a chocolate mousse she had made. “I’ve always had a problem with that method,” he said. “Think about it: it means that a few generations down the road, the entire population is descended from that one lucky mutant. You end up with a very small gene pool that way, and that tends to concentrate recessive genetic disorders.” He handed a glass bowl to Klimus, then sat down. “It’s like Queen Victoria, who carried the hemophilia gene. Her offspring inbred with the royal houses of Europe, devastating them. To suppose that whole populations are reduced to a single parent every time a major mutation-driven advantage occurs would make life extraordinarily precarious. If an accident didn’t kill off the lucky mutant, his or her offspring might die off anyway through genetic diseases.” He sampled the mousse, then nodded, impressed. “Now, if evolution could somehow occur simultaneously across widely dispersed populations, as the multiregionalists are suggesting, well, I suppose that would avoid that problem — but I can’t think of any mechanism that would allow that kind of evolution, although—”

Amanda started crying. Pierre immediately got back on his feet and hurried over to her, picking her up, holding her against his shoulder, and bouncing her up and down gently. “There, there, honey,” he cooed. “There, there.” He smiled at Klimus, back in the dining room. “Sorry about this,” he said.