Stephen Baxter's reputation precedes him. Perhaps more than any other contemporary science fiction author, Baxter deals in the grand sweep—of time, of space—and the vertiginous distance. A small scale for Baxter is an alternate history of the British Isles over mere hundreds of years, as found in his Time's Tapestry quartet; the span of his Xeelee sequence, meanwhile, can be counted in the billions. It is impossible to approach a new Baxter novel, whatever your familiarity with the detail of his oeuvre, without sparing half a thought for its grander project.

Inevitably, Baxter's latest, Stone Spring, is indeed part of a bigger picture, the first novel in another alternate history series. This putative "Northland saga" begins in 8,000 BC, deep in the Mesolithic period, and will end in 1500, in a Northern Europe transformed by the actions of the tribes featured in Stone Spring: one that will never have known the Roman Empire, Christianity, or Islam. The great strength of these big ideas is obvious: their sense of wonder; their ability to get under the skin of what we think we know about ourselves, of our pasts and futures. The great weakness is that they encourage gluttony: rather than sampling and enjoying the constituent novels, even scenes, in and of themselves, the reader of Baxter might be tempted always to ask for the next course, never to be happy until, fit to burst, the entire meal has been devoured.

In the case of Stone Spring, this would in many ways be something of a pity: it is often a strikingly intimate novel, taking place over a Mesolithic lifetime of thirty-three years and focusing with some care on the lives of a knot of tribespeople living on the great land corridor between what would become Britain and modern Holland, known to modern scholars as Doggerland but to the characters of Stone Spring as Northland. The first third of the novel, possibly its best section, deals with bringing together these individuals: Ana, her sister Zesi, and the other inhabitants of Etxelur, an important meeting point between Pretani and the rest of the Northland; Ice Dreamer, a Palaeo-American tribeswoman rescued from the destruction of her people by the Archaic cultures and brought across the Atlantic by Ana's father; and Novu, an inhabitant of Jericho, the world's sole city, who is indentured to a prehistoric travelling salesman and finds his way to Doggerland.

As these disparate origins might imply, Baxter is very much interested in how Mesolithic society might have functioned at quite an advanced level. He takes time carefully to depict a varied array of human cultures—patriarchal and less so, urban and hunter-gatherer, a whole slew of religious and spiritual beliefs—and in so doing crafts a quite convincingly limited, but far from primitive, civilization. The contacts between Baxter's various tribes are irregular—there are innumerable different tongues, and members of different tribes can often communicate only in a rudimentary trader's patois—and, certainly, there are some quite brutal and unattractive cultures represented; yet by the same token this Mesolithic is no dark age. In depicting humans living fairly well in deeply difficult circumstances, Stone Spring is in its own way as great a paen to human ingenuity and capacity as any fantasised space age.

Last year I reviewed for Strange Horizons Nicholas Ruddick's superlative study of prehistoric fiction, The Fire in the Stone. Baxter has quite clearly familiarised himself if not with Ruddick's work then at the very least the lessons he drew from the patchy history of this curious subgenre: many writers of prehistoric fiction, Ruddick suggested, have made glaring and unforced errors, projecting with abandon onto the distant and unknowable past their own preconceptions, assumptions, and prejudices. This makes prehistoric fiction a rich source of information about such cultural mores, but often less successful as a forum for the practice of imaginative sympathy. Baxter cannot be accused of lacking this latter quality: Stone Spring is alive to the humanity of prehistoric peoples, and all we have in common with them. In this, he follows William Golding, who in The Inheritors (1955) breathed vivid life into Neanderthals, depicting their sophisticated rituals and communities; but whereas Golding slowly revealed the limits of the Neanderthals' particular ways of living, the core of Baxter's novel—and indeed the series it commences—is the concept that Mesolithic peoples may have had the power to halt the great flood which submerged Doggerland and isolated Britain.

It might be said, then, that Stone Spring is closer to the work of Jean M. Auel, who in The Clan of the Cave Bear (1980) and its many sequels posits a prehistoric Earth in which the people think, speak, and in large part do much as we might. The Clan of the Cave Bear is set around 10,000 years prior to Baxter's novel, but Stone Spring can be just as easily characterised as "soap opera," the judgement of Auel's work delivered by the unsympathetic literary critic Joseph Carroll. From the novel's strong female lead to, in Brian Robb's words, its strong whiff of Dallas, Stone Spring shares an aesthetic with Auel, even an appeal to a similar market. At times, there is no doubt, this emphasis throws the reader out of Baxter's prehistoric milieu: in the bickering of the Etxelur sisters, Ana and Zesi ("I wish I had your wisdom." "I wish I had your eyebrows." [p. 174]), we are transported to the twenty-first-century bedrooms of teenage girls; meanwhile, as Adam Roberts has pointed out, the reverence for babies exhibited by many of the characters would probably be out of place in 1500, let alone at the dawn of Baxter's saga. There is real density to Baxter's worldbuilding which is by and large convincing, but his project cannot avoid these wobbles.

Fortunately, the lengths to which Baxter goes to give his characters personalities which might engage his readers' sympathies is also the real strength of the novel. Stone Spring is very much a family saga, beginning with Ana's coming of age and ending in her twilight years, and following the fate of three generations of her family and the land which is so important to them. If this is soap opera, it is accomplished soap opera, and the various twists and turns of personal narrative provide the novel's real grit. Admittedly, they do at times also recall the extreme personality transplants inherent in the genre: at one point, Ana laments events without which the Pretani visitor, Shade, "would still be the bright, curious, loving boy she had met, instead of the bitter thing he had become in the course of a single summer" (p. 267). Ana's sister, too, will be transformed by various travails from a headstrong but dutiful tribeswoman into the cruellest, most vengeful character in the book. If these changes are not quite convincing, they are at least vividly done—and, in the best traditions of soap opera, succeed in keeping the story moving.

Because move it does. When Novu, the refugee from the brick city of Jericho, arrives in Etxelur, he soon begins to introduce the curious innovations of his people to Ana's. It is clear from the way in which Baxter measures time in this novel—by a given event's proximity to an approaching "Great Sea"—that this technology will come to be important. This not least because Baxter is no stranger to floods—his most recent books, Flood (2008) and Ark (2009), were near-future disaster novels with an awful lot of water. Indeed, it's hard at times not to read Stone Spring as a kind of allegory—the Etxelur peoples' very origin myth speaks of a land "too full of mouths" to which "death" is given as a result (p. 49), whilst the work of "many generations" which has built the middens used to store the Etxelur dead is to be wiped away because "the sea is taking back the land" (p. 25). The threat to our own civilization from rising sea water hangs ever above Baxter's prehistoric apocalypse. As Novu and the others begin to build brick defences against the tide, we begin to hear something of a call to action.

So it is that the soap opera supports the speculation: when one character speaks of his "deep human core" (p. 55), or another is wise enough to realise that "we have to find a balance between the needs of the present and this plan for the future" (p. 307), the odd way in which Baxter allows us to see ourselves in his Mesolithic tribespeople provides his speculative flourishes with real relevance. It is the novel's central coup, then, that it thoroughly imagines a prehistoric, entirely alien world, and yet at the same time lends pertinence to its distant and, for us, quite natural main event—the submergence of Doggerland. On the very first page of Stone Spring, Baxter tells us of the Etxelur landscape that "there was rarely a trace of forgotten ancestors." His aim is to remind us of ourselves.

It's something of a shame, then, that Stone Spring outstays its welcome a tad. The novel has the feel of one eminently editable. Though episodes in Pretani introduce the fascinating Leafy Boys, feral tree-dwelling humans who steal other tribes' toddlers rather than reproduce themselves, there is a sense that these are over-long and over-detailed; likewise, the elision which is part of Baxter's narrative strategy throughout becomes more and more pronounced as the book continues—the first 320 pages cover a little over a year in time, whilst the 140 pages following cover another 32, producing a sense of successive epilogues drawing out the main body of story. Some of the nicest, and nastiest, writing occurs in these sections—Baxter is very good at the violence of prehistoric life—and yet they nevertheless render the novel in some way imbalanced. There are such dips in the tautness of the story throughout, and though Baxter usually manages to conjure another hook, there were chapters at a time which felt to be treading water. At one point, Baxter takes three paragraphs to tell me no one turned up to a tribe council except a dog (p. 296). You can do it in eleven words.

Nevertheless, Stone Spring does more with much of its length. In large part, this is a novel about understanding, and allowing for, the other. "I see an edge," one character says to Anna of Etxelur. "You see a centre. Can a world have two centres?" (p. 216) There are so many centres in the novel—or at least so many places perceived by someone or other as a centre—that the only possibly answer to this question is "yes." Ana's success in leading her people in the effort to hold back the seas is made possible only by cooperation between a number of tribes; one of novel's most sympathetic characters, Jurgi the priest, is used to explore an ecumenical approach to religion and spirituality; and the great villain of the piece is egoism—the brutish Pretani, for instance, are conceited enough to name their whole peninsula after themselves, "though they are only one tribe amongst dozens, hundreds" (p. 179). Even Ana, in many ways the hero of the novel, displays a vain self-confidence which has a corrosive effect on her people: "It was as if the rebuilding of Etxelur had become a madness that was eating all their lives, and turning them away from the wisdom of the mothers" (p. 353).

This ambivalence towards the side effects of technological development adds a satisfyingly contrary note to what could more simply have been a straightforward hymn to progress. Stone Spring is an engaging and evocative novel of some depth. Not only that, it is a memorable and by and large successful imagining of a prehistoric world. In The Fire in the Stone, Nicholas Ruddick argued, "The study of human origins is a highly speculative discipline." There are few speculators in fiction with a greater reputation for boldness and breadth than Stephen Baxter. Stone Spring doesn't reinvent his wheel, but barring a few potholes it spins perfectly well regardless.

Dan Hartland blogs at http://thestoryandthetruth.wordpress.com.