I daresay that, even in the 21st century, there are explorers who serve a useful function  Pen Hadow comes to mind, leading scientists across the Arctic. But from the point of view of our dear old abused and shrunken planet, they do now seem entirely unnecessary. Worse, they might be a distraction  I'm thinking of the antics of the adventurers you see dumbed down on the telly. No, the type who calls himself an "explorer" today is, when you come to think about it, as likely as not a sort of middle-class vainglorious athlete; he's a dilettante, but with communication skills, the fortitude possessed by any half-decent soldier, and a flair for self publicity  while the real business of discovery is being done by the boffin scratching at a rock sample or staring into an electron microscope. Yet our public schools still churn them out, these explorer types  I suppose I mean types like me. And for what purpose? We strut and fret, showing ourselves off upon the world stage while that stage burns.

These were my gloomy reflections as I opened The Great Explorers, a collection of biographical essays on many of the great names from past to present  Columbus, Vasco da Gama, Alfred Russel Wallace, Amundsen, each according to their terrain. There were surprises (the illustrator Thomas Baines and the desert motorist Ralph A Bagnold), and these enriched the whole. There were also notable absences: no Captain Scott. This will be a shocker for many readers, especially those who recall that, though he made a hash of claiming the south pole, Scott had a greater scientific programme than Amundsen. Rather too keen on the manly art of sledge-hauling certainly, but what is exploration if not discovery, and what person better expressed the struggle and sacrifice of the pioneer? Instead, we must be satisfied with Amundsen  effective, clinical, intellectually modern.

Which is ironic, because this book in all three regards is exactly the opposite. It's the type you curl up in the chair with. It's a glorious, but visually rather cramped, nostalgia-fest that makes even recent figures such as Jacques Cousteau appear from an era long gone. Exploration, the message seems to be, belongs in the cosy world of yesteryear.

And thus we return to my central question: what, actually, is the point of the modern-day explorer? The very same was asked not long ago at the Royal Geographical Society, which now prefers to encourage hard-edged research rather than the glorious expeditioning of past times.

Believing the august body to have lost its way, Robin Hanbury-Tenison mentored the Beagle Campaign, a lobbying group which aimed to put the RGS right. The bitter truth is, however, that for Richard Burton, Hernando de Soto, Livingstone and many more of the romantic characters represented in the book, their justification remained strictly scientific, imperial or financial. We all wanted to believe in the campaign, and many of us signed up to it. But in the end, reality prevailed. The "Beaglers'" battle was not with the current regime at the RGS, but with the march of time. Once, generalists like us were useful  we communicated what was unknown to our people back home; some characters such as Fridtjof Nansen and Ernest Shackleton, as well as Hanbury-Tenison himself, also galvanised and organised scientific endeavour. But that time, sad to say, is fast passing.

The Beagle Campaign was existentially flawed, and so is this book: absorbing, factually tight, sensitive to its Eurocentricity, it gathers together a host of valuable essays. Things only start to look wobbly towards the present day.

Would Bagnold's sand-dune studies have earned a place in any other century? And does the young arctic venturer Gino Watkins really compare to Sir Douglas Mawson, who bequeathed his Australia and our world so much of Antarctica? The authorship of the later essays  there's a "New Frontiers" section  also becomes untidy. Cousteau's underwater legacy is detailed by his son Jean-Michel, but being part of that legacy he finds himself writing up his own exploits  and all in the third person, as if in self-admiration.

The book closes with the distinguished caver Andrew Eavis, who tells his own story in the first person. And because he is not the most accomplished author here  other contributors include Anthony Sattin and Alexander Maitland  the result is that one of our supreme living explorers ends up ill-served, while the book's end is rendered limp.

Where does all this leave the modern-day pioneer? Hanbury-Tenison's dust jackets are invariably adorned with a startling quote from 1982 that he is "the greatest explorer of the past twenty years"  up yours, Eavis  and the more recent line that he is the "doyen of British explorers" (stuff you, Sir Ranulph). The RGS knows better. Exploration, or whatever you choose to call the business of going out to research the unknown, has moved on from the likes of us. Although the author knows this, and says it  "We are only now starting to realise how little we understand the workings of nature"  he seems not to want to believe. There's nothing here on the exploration by specialists of our seabeds, which comprise two-thirds of our planet, or the innumerable scientists the RGS still sends out  a greater number of projects than ever.

Here's the thing: at one level, the frontiers now rightly belong to seriously important researchers, such as the oceanographer Robert Ballard and the primatologist Jane Goodall. At another, exotic travel is no longer the preserve of a few privileged and romantic males. You do not need us; we are all explorers now.

Benedict Allen's Into the Abyss: Explorers on the Edge of Survival is published by Faber.