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2it didn鈥檛 last。
after about a decade of parative calm； paleoanthropology embarked on another periodof swift and prolific discovery； which hasn鈥檛 abated yet。 the 1960s produced homo habilis；thought by some to be the missing link between apes and humans； but thought by others not tobe a separate species at all。 then came （among many others） homo ergaster； homolouisleakeyi； homo rudolfensis； homo microcranus； and homo antecessor； as well as a raft ofaustralopithecines： a。afarensis； a。 praegens； a。 ramidus； a。 walkeri； a。 anamensis； and stillothers。 altogether； some twenty types of hominid are recognized in the literature today。
unfortunately； almost no two experts recognize the same twenty。
some continue to observe the two hominid genera suggested by howell in 1960； but othersplace some of the australopithecines in a separate genus called paranthropus ； and still othersadd an earlier group called ardipithecus。 some put praegens into australopithecus and someinto a new classification； homo antiquus； but most don鈥檛 recognize praegens as a separatespecies at all。 there is no central authority that rules on these things。 the only way a namebees accepted is by consensus； and there is often very little of that。
a big part of the problem； paradoxically； is a shortage of evidence。 since the dawn of time；several billion human （or humanlike） beings have lived； each contributing a little geneticvariability to the total human stock。 out of this vast number； the whole of our understandingof human prehistory is based on the remains； often exceedingly fragmentary； of perhaps fivethousand individuals。 鈥測ou could fit it all into the back of a pickup truck if you didn鈥檛 mind2humans are put in the lamely homimdae。 its members； traditionally called hominids； include any creatures（including extinct ones） that are more closely related to us than to any surviving chimpanzees。 the apes；meanwhile； are lumped together in a family called pongidae。 many authorities believe that chimps； gorillas； andorangutans should also be included in this family； with humans and chimps in a subfamily called homininae。
the upshot is that the creatures traditionally called hominids bee； under this arrangement； hominins。 （leakeyand others insist on that designation。） hominoidea is the name of the aue sunerfamily which includes us。
how much you jumbled everything up；鈥潯an tattersall； the bearded and friendly curator ofanthropology at the american museum of natural history in new york； replied when i askedhim the size of the total world archive of hominid and early human bones。
the shortage wouldn鈥檛 be so bad if the bones were distributed evenly through time andspace； but of course they are not。 they appear randomly； often in the most tantalizing fashion。
homo erectus walked the earth for well over a million years and inhabited territory from theatlantic edge of europe to the pacific side of china； yet if you brought back to life everyhomo erectus individual whose existence we can vouch for； they wouldn鈥檛 fill a school bus。
homo habilis consists of even less： just two partial skeletons and a number of isolated limbbones。 something as short…lived as our own civilization would almost certainly not be knownfrom the fossil record at all。
鈥渋n europe；鈥潯attersall offers by way of illustration； 鈥測ou鈥檝e got hominid skulls in georgiadated to about 1。7 million years ago； but then you have a gap of almost a million years beforethe next remains turn up in spain； right on the other side of the continent； and then you鈥檝e gotanother 300；000…year gap before you get a homo heidelbergensis in germany鈥攁nd none ofthem looks terribly much like any of the others。鈥潯e smiled。 鈥渋t鈥檚 from these kinds offragmentary pieces that you鈥檙e trying to work out the histories of entire species。 it鈥檚 quite atall order。 we really have very little idea of the relationships between many ancient species鈥攚hich led to us and which were evolutionary dead ends。 some probably don鈥檛 deserve to beregarded as separate species at all。鈥�
it is the patchiness of the record that makes each new find look so sudden and distinct fromall the others。 if we had tens of thousands of skeletons distributed at regular intervals throughthe historical record； there would be appreciably more degrees of shading。 whole new speciesdon鈥檛 emerge instantaneously； as the fossil record implies； but gradually out of other； existingspecies。 the closer you go back to a point of divergence； the closer the similarities are； so thatit bees exceedingly difficult； and sometimes impossible； to distinguish a late homoerectus from an early homo sapiens； since it is likely to be both and neither。 similardisagreements can often arise over questions of identification from fragmentary remains鈥攄eciding； for instance； whether a particular bone represents a female australopithecus boiseior a male homo habilis。
with so little to be certain about； scientists often have to make assumptions based on otherobjects found nearby； and these may be little more than valiant guesses。 as alan walker andpat shipman have drily observed； if you correlate tool discovery with the species of creaturemost often found nearby； you would have to conclude that early hand tools were mostly madeby antelopes。
perhaps nothing better typifies the confusion than the fragmentary bundle of contradictionsthat was homo habilis。 simply put； habilis bones make no sense。 when arranged in sequence；they show males and females evolving at different rates and in different directions鈥攖he malesbeing less apelike and more human with time； while females from the same period appearto be moving away from humanness toward greater apeness。 some authorities don鈥檛 believehabilis is a valid category at all。 tattersall and his colleague jeffrey schwartz dismiss it as amere 鈥渨astebasket species鈥濃�攐ne into which unrelated fossils 鈥渃ould be conveniently swept。鈥�
even those who see habilis as an independent species don鈥檛 agree on whether it is of the samegenus as us or is from a side branch that never came to anything。
finally； but perhaps above all； human nature is a factor in all this。 scientists have a naturalten