From the earliest modern humans to the present day, our species has evolved dramatically in both biological and behavioural terms. What forces prompted these momentous changes?

Reading Passage 2 has six sections, A–F.

Kenya has long been known as the 'cradle of mankind' following the discovery of fossils thought to be of the first members of the human family, which arose in Africa around 6–7 million years ago. Various distinct species evolved from these ancestors over millions of years, including our own – Homo sapiens – around 250,000 years ago. 'A lot of the research on the origins of modern humans has focused on defining their point of origin, then understanding why humans left Africa about 60,000 years ago to colonise the rest of the world,' says anthropologist Dr Marta Mirazón Lahr of Cambridge University. 'But we have no idea what happened between 200,000 years and 60,000 years ago. We also have very little information on what occurred inside Africa after 60,000 years, when the different population groups and languages we see today evolved. The genetics suggest that the expansion out of Africa is just the tip of a massive population expansion inside the continent.'

Along with fellow Cambridge anthropologist Professor Robert Foley, Mirazón Lahr is investigating the evolutionary history of modern human populations. 'The challenge is to find the sites where evidence of these early people can be recovered – their stone tools, the animals they hunted, their ornaments and, ultimately, the fossils of the people themselves,' she says. She has chosen to focus on East Africa based on the theory that its past environment was suitable for sustained occupation over time. But the region is huge, and finding the right place to look is absolutely crucial. 'In the past there were periods of enormous rainfall in the tropics,' she says. 'The lakes were much higher and their margins were wider. We are looking at where the ancient lake margins would have been when the lakes were last high, and that's where we look.'

Some of their most spectacular finds have been on the ancient Turkana beaches in Kenya's Rift Valley. 'Ten thousand years ago, this area was wetter, with animals such as gazelles, hippos and lions, and the beaches are still there, even though the lake is long gone. We've found a great many shells on the surface, and a small number of harpoons the people fished with. A lot has already been exposed by the wind, and occasionally we find sites where things are buried, and then we dig,' she says. 'We're looking at the stone tools and how these relate to times of particularly high water levels. Then we're looking at the fauna and, if we're lucky, we find actual human fossils. The oldest fossil ever found that looks like a modern human is 200,000 years old, and comes from the Turkana Basin. We're trying to find the fossils that mark the origin of Homo sapiens.'

The primitive technologies that our early ancestors left behind gradually evolve, and comparing finds dated to different times can advance understanding of our own evolutionary trajectory. 'We think the evolution to modern humans is associated with changes in behaviour and in technology, for example in their tool use. We've already found evidence that they started using animal bones to make tools, which was rare in earlier populations,' says Mirazón Lahr. 'The people who lived around here 10,000 years ago used microliths – a form of miniaturised stone tool technology,' adds her colleague Foley. 'Instead of producing one or two big flakes like the earliest modern humans, they produced lots of very small flakes to make composite tools. We've also found a beach in the Turkana Basin from about 200,000 years ago and that has its own very different fossilised fauna, and very different stone tools. The technology and the people changed a lot during the past 200,000 years.'

Mirazón Lahr emphasises that geography and climate played a critical role in the origins and diversification of modern humans. 'The times when the lakes were high were periods of plenty in East Africa,' she says. 'When it was very wet there were lots of animals to hunt, the vegetation could grow, and you can imagine that the people would have thrived.' East Africa had a unique mosaic environment with lake basins, highlands and plains that provided alternative niches for foraging populations over this period. 'We think that early modern humans could live in the region throughout these long periods, even if they had to move between basins.' With a network of habitable zones, human populations survived by expanding, contracting and shifting ranges according to the state of the environment at any given time.

By comparing the fossil records from different basins over time, Mirazón Lahr is trying to establish a spatial and temporal image of human occupation over the past 200,000 years. She believes that the way to find novel insights is to consider each problem from various angles. Drawing on her wide-ranging interests from molecular genetics to prehistory, and combining genetic, fossil, archaeological and palaeoclimatic information, she hopes to form an accurate and complete picture of our early ancestors' lives and the external forces that shaped their evolution, both biological and behavioural.

While the Nobel Prizes are over 115 years old, rewards for scientific achievement have been around much longer. As early as the 17th century, at the very origins of modern experimental science, promoters of science realized the need for some system of recognition and reward that would provide incentive for advances in the field.

Before the prize, it was the gift that dominated in science. Precursors to modern scientists – the early astronomers, philosophers, physicians, alchemists and engineers – offered wonderful discoveries, inventions and works of literature or art as gifts to powerful patrons, often royalty. Many scientists prefaced their publications with extravagant letters of dedication; they might, or they might not, be rewarded with a gift in return. Eventually, different kinds of incentives, including prizes and awards, as well as new, salaried academic positions, became more common and the favor of particular wealthy patrons diminished in importance. But at the height of the Renaissance, early scientists relied on gifts from powerful princes to compensate and advertise their efforts.

With courtiers all vying for a patron's attention, scientific gifts had to be presented with drama and flair. The astronomer Galileo Galilei (1564–1642) presented his newly discovered moons of Jupiter to the Medici dukes of Italy as a 'gift' that was literally out of this world. In return, the Medici family 'ennobled' Galileo with the title and position of court philosopher and mathematician. If a gift succeeded, the gift-giver might, like Galileo in this case, be fortunate enough to receive a gift in return. Gift-givers could not, however, predict what form a patron's gift would take, and they might find themselves burdened with offers they couldn't refuse. Tycho Brahe (1546–1601), the great Danish Renaissance astronomer, received everything from exotic animals to chemical secrets in return for his discoveries.

By the early-17th century, scientific promoters realized that gift-giving was ill-suited to encouraging experimental science. Experimentation required many individuals to collect data in many places across long periods of time. Gifts emphasized competitive individualism at a time when scientific collaboration and the often humdrum work of empirical observation were paramount.

While it was accepted that some competitive rivalry helped to inspire and advance science, scientific reformers believed that too much led to the ostentation that too often plagued courtly gift-giving. Most of all, reformers feared an individual would not tackle a problem that couldn't be finished and presented to a patron in his or her lifetime – or even if they did, their findings might die with them.

For these reasons, promoters of experimental science saw the reform of rewards as integral to radical changes in the pace and scale of scientific discovery. For example, Sir Francis Bacon (1561–1626), lord chancellor of England and an influential booster of experimental science, emphasized the importance even of 'approximations' or unfinished attempts at reaching a particular goal. Instead of dissipating their efforts attempting to appease patrons, many researchers, he hoped, could be stimulated to work toward the same ends via a well-publicized research wish list. Bacon coined the term 'desiderata', still used by researchers today to denote widespread research goals. He also suggested many ingenious ways to advance discovery by stimulating the human hunger for fame; a row of statues celebrating famous inventors of the past, for example, could be paired with a row of empty plinths upon which researchers might imagine their own busts one day resting.

Bacon's techniques inspired one of his chief admirers, the reformer Samuel Hartlib (circa 1600–1662) to collect many schemes for reforming the system of recognition. One proposed that rewards should go not only 'to such as exactly hit the marke, but even to those that probably misse it', because their errors would stimulate others and make 'active braines to beate about for New Inventions'. Hartlib planned a centralized office systematizing rewards for those who 'expect Rewards for Services done to the King or State, and know not where to pitch and what to desire'.

Collaborative scientific societies, beginning in the mid-17th century, distanced rewards from the whims and demands of individual patrons. The periodicals that many new scientific societies started publishing offered a new medium that allowed authors to tackle ambitious research problems that might not individually produce a complete publication pleasing to a dedicatee. The societies saw their periodicals as a means to entice discovery by offering credit. Today's Leopoldina, the German national scientific society, founded its publication in 1670. According to its bylaws, those who might not otherwise publish their findings could see them 'exhibited to the world … with the praiseworthy mention of their name' – an important step on the way to standardizing scientific citation.

States might also offer rewards for solutions to problems, most famously in the case of the prize offered by the British government in 1714 for figuring out how to determine longitude at sea. Some in the 17th century likened this long-sought discovery to the philosopher's stone. The idea of using a prize to highlight a specific problem is alive and well today. In fact, some contemporary scientific prizes, such as the Simons Foundation's 'Cracking the Glass Problem', set forth specific questions that still need to be resolved.

The shift from gift-giving to prize-giving completely transformed the rules of engagement in scientific discovery. Of course, the need for monetary support hasn't gone away. Obtaining financial support can still be a sizable part of what it takes to get science done today. Succeeding in grant competitions might seem mystifying, and winning a career-changing Nobel might come as a bolt out of the blue. But researchers can take comfort that they no longer have to present their innovations on bended knee as wondrous gifts that will appeal to the whims of individual patrons.