This is a side story in Leo Frankowski's Conrad Stargard series, following various people blamed for stranding Conrad, a relative of the owner of a time travel company, in medieval Poland. The first book has a female researcher making the initial error that results in Conrad's trip through time. The later books all open with her, and her superior, dealing with the punishment.
From The High-Tech Knight, book 2:
"You weren't briefed? This is anthropological research station fifty-seven. The time is half past two.
million B.C., and I am your charming host, Robert McDougall. I'd tip my hat, but you see the problem.
The tribe here calls me 'Gack,' so you might as well, too. No point in being formal when you're naked.
I'll be your boss for the next fifty years.
....
"All part of the high price of science," he said. But she had pulled herself into a fetal position and was
sobbing louder. "Hey, you're serious, aren't you? You actually didn't volunteer for this post?"
"No! I mean, yes I didn't volunteer. I was in twentieth-century Poland. I spent one day on my new
assignment and the monitors came and I woke up here! I'm in the Historical Corps. I don't know
anything about anthropology!"
From The Radiant Warrior, book 3:
"Surprise! You son of a bitch!" she shouted. "Welcome to two and a half million B.C.! Welcome to a
hundred years of dodging leopards and eating grubs and shivering up in a tree all night, you bastard,
because it's all your fault!"
"What? Where am I?"
"The where is eastern Africa, you lucky boy, but the fun part is the when! You're in the Anthropological
Corps now and you get to do the exciting work of tracking protohuman migration patterns!"
"This must be some sort of a joke! And you are the rudest and the ugliest woman I've ever seen!"
"Watch your language, buster! I'm your boss and will be for the next fifty years. And if you think I'm ugly,
just wait until you see yourself in a mirror, not that we have one."
From The Flying Warlord, book 4:
"Whoopee shit! . . . It's finally happening," she said. "A hundred years of tracking protohuman migration patterns on the African plain and it's finally over! It feels so good that I almost don't hate your guts anymore!"
"Well, don't get too carried away. You deserved every minute of it for dumping the owner's cousin into the thirteenth century when the guy didn't even know that time travel existed. And you deserve twice that for getting me messed up in it. Now get your scrawny body in the box. Time's running short!"
"Eat your heart out! I'll have my old sexy body back, and I'll take bubble baths and while you're eating carrion, I'll gorge for weeks on lobster thermidor and New York cheesecake and—"
....
She stared at him and then at the other stasis chamber.
The body within was shriveled and dried. It was laying on its side, a look of horror on its face. Its fingernails were all ripped off as if the man had tried to claw his way out before his air was exhausted.
From Lord Conrad's Lady, book 5:
On the lush African plain, at two and a half million years B.C., two small brown individuals were sitting
naked on a small hill. To all outward appearances they were a pair of type twenty-seven proto-humans.
“There’s blood on your leg,” he said.
“I’m menstruating. The antifertility vaccine is wearing off. It’s been a hundred and eighty years, and the
shot was only supposed to last a century.”
....
“Well, there’s something we ought to talk about. We’re getting old. Before too many more years, we
won’t be able to take care of ourselves anymore. If we stay with the protos, they’ll treat us the same way
they treat their own parents when they get too old to be useful. They’ll just abandon us,” he said.
“So?”
“So we have to do something about it! We have to make sure that there’s somebody around to take care
of us when we get really old. See, my antifertility shots have worn off, too. For the next few years you
can still have children, and I’m still fit enough to take care of you and them. If we raise them right, they’ll
take care of us when it really gets bad.”
Frankowski dropped the plotline from the sixth book on.
