A meteorology professor stood before his Meteorology 101 class and had some items in front of him. When the class began, wordlessly he picked up a very large and empty glass mayonnaise jar and proceeded to fill it with golf balls. He then asked the students if the jar was full. They agreed that it was.

The professor then picked up a jar of pebbles and poured them into the jar. He shook the jar lightly. The pebbles, of course, rolled into the open spaces between the golf balls. He then asked the students again if the jar was full. They agreed it was.

The professor picked up a box of sand and poured it into the jar and of course the sand filled up everything else. He asked once more if the jar was full. The students responded with an unanimous yes.

The professor then produced two cans of beer from under the table and then proceeded to pour the entire contents into the jar, effectively filling the empty space between the grains of sand. The students laughed.

"Now," said the professor, as the laughter subsided, "I want you to recognize that this jar represents your life. The golf balls are the important things -- your family, your partner, your health, your children, your friends, your favorite passions -- things that if everything else was lost and only they remained, your life would still be full.

"The pebbles are the other things that matter, like your job, your house, your car. The sand is everything else -- the small stuff.

"If you put the sand into the jar first," he continued, "there is no room for the pebbles or the golf balls. The same goes for your life. If you spend all your time and energy on the small stuff, you will never have room for the things that are important to you. Pay attention to the things that are critical to your happiness. Play with your children. Take time to get medical checkups. Take your partner out dancing. Play another 18.

"There will always be time to go to work, clean the house, give a dinner party and fix the disposal. Take care of the golf balls first -- the things that really matter. Set your priorities. The rest is just sand."

One of the students raised her hand and inquired what the beer represented. The professor smiled. "I'm glad you asked. It just goes to show you that no matter how full your life may seem, there's always room for a couple of beers."

Once-Balmy Climate Lured Humans to England Early.

By Ann Gibbons

Scientists following a trail of stone tools and butchered animal bones have uncovered evidence that early humans lived in Britain well before 500,000 years ago, perhaps not long after the first Europeans appear much farther south in Spain and Italy, about 800,000 to 1 million years ago. The early English settlers probably followed a wave of hippos, elephants, hyenas, and other animals drawn to Britain’s then-balmy climate, according to a talk and poster by paleoanthropologist Chris Stringer of the Natural History Museum in London. But when the climate cooled, as it did repeatedly over the following epochs, all traces of human occupation vanished.

Several new sites suggest that humans were in Britain well before the appearance of the 500,000-year-old Boxgrove Man, whose shinbone and teeth were discovered in a gravel quarry in Boxgrove, England, from 1993 to 1996. The sites may help shed light on whether more than one type of human migrated to Europe more than 500,000 years ago and reveal the type of terrain they could inhabit. “This pushes the age of humans north of the Alps back further than previously documented,” says paleoanthropologist Erik Trinkaus of Washington University in St. Louis, Missouri.

Boxgrove showed that the earliest known Briton was a member of Homo heidelbergensis, a proto-Neandertal species with deep roots in Europe. The new sites have no human remains, but researchers found tools along the coast of the ancient Bytham River in East Anglia. The tools appear in some of the most ancient river terraces and are associated with insects and animals that suggest a date far older than Boxgrove, Stringer said in his talk. One site with tools may be as old as 700,000 years.

These early Europeans carried a primitive stone tool kit for scraping and cutting. But they lacked the hand ax—a versatile stone tool nicknamed the Paleolithic Swiss Army knife—already in widespread use in Africa. The Boxgrove hominid did wield a hand ax and so may have been part of a separate wave of settlers, says Stringer, who directs the $1.88 million Ancient Human Occupation of Britain program funded by the Leverhulme Trust. Studies of animal fossils paint a portrait of a warm climate that allowed animals now found only in Africa to migrate from northern Europe to England across a land bridge.

Although humans arrived in Britain early, they did not live there continuously, said Stringer. There are no signs of human occupation during several periods, particularly during glaciations. From 180,000 to 130,000 years ago, herds of mammoth and reindeer roamed England, but there is little evidence of humans. Hippos and elephants reappear when the ice caps melt at about 130,000 years, but humans don’t show up again until about 60,000 years ago when Neandertals return. Modern humans came later, but even they disappeared during an Ice Age as recent as 25,000 to 17,000 years ago. “People assume that once people were in Britain, they were always there,” says Stringer. “We’re seeing little pulses of human occupation. They disappeared when it got very cold. There is not a continuous human presence until 12,000 years ago.”