LETTERS 



Warning Scents? 



Uldis Roze ["Smart 

 Weapons," 3/06] and his 

 colleagues identified R- 

 delta-decalactone as the 

 chemical behind the scent 

 of an angry porcupine. But 

 how can they be sure that 

 the other components of 

 the scent were unimpor- 

 tant? Perhaps nonhuman 

 animals smell things that to 

 a person are odorless. Or, 

 perhaps other parts of the 

 porcupine odor register 

 more strongly in nonhu- 

 man animals. 

 Colin MacKenzie 

 Mission Hills, California 



Uldis Roze replies: Colin 

 MacKenzie s point is well 

 taken. Of the thousand or so 

 olfactory receptor (OR) 

 genes in the mammalian 

 genome, roughly 60 percent 

 are turned off (encoded as 

 pseudogenes) in humans. 

 That percentage is far higher 

 than the corresponding per- 

 centage in other mammals 

 that have been tested. But 

 since the OR genes for R- 

 delta-decalactone have not 

 been turned off in humans, 

 they must be important for 

 survival, and they probably 

 have not been turned off in 

 other mammals either. 

 Hence for other mammals, 

 the olfactory portrait of a 

 porcupine might include ad- 

 ditional notes, but it is prob- 

 ably not missing a note of 

 R-delta-decalactone. 



The porcupine has cho- 

 sen well in basing its warn- 

 ing system on that chemical. 

 Besides being universally 

 recognized by potential 

 mammal predators, R-delta- 

 decalactone is volatile, un- 

 usual, and present in high 

 enough concentrations to 



pack the desired punch. No 

 other component of the 

 warning mixture can claim 

 all those features. 



Ancestral Disputes 



Russell L. Ciochon and 

 Gregg F. Gunnell ["Our 

 Anthropoid Roots," 03/06] 

 claim that recently discov- 

 ered fossils contradict the 

 longstanding view that am- 

 phipithecid primates lie near 

 the base of the anthropoid 

 lineage. Actually, improved 

 knowledge of amphipithe- 

 cid anatomy strengthens 

 their anthropoid status. 



In contrast to adapoids 

 and other primitive pri- 

 mates, anthropoids had a 

 reduced reliance on the 

 sense of smell. As a result, 

 the snouts and jaws of early 

 anthropoids were compact- 

 ed, yielding a more abbre- 

 viated, monkeylike face. 

 Amphipithecid jaws reflect 

 that distinctive evolutionary 

 change: their lower premo- 

 lars are reduced and crowd- 

 ed in a way that never oc- 

 curs in adapoids. No com- 

 petent paleontologist would 

 confuse amphipithecid jaws 

 with those of adapoids. 



Amphipithecids and other 

 fossil primates show that the 

 roots of our extended family 

 tree germinated in Asia mil- 

 lions of years earlier than 

 was previously thought. 

 Chris Beard 

 Carnegie Museum 



of Natural History 

 Pittsburgh , Pctmsylvania 



On page 56, Russell Cio- 

 chon and Gregg Gunnell 

 present a graphic summary 

 of traits that distinguish 

 prosimians and anthro- 

 poids. But they omit the 

 ectotympanic, an "ear 



bone" that occurs in two 

 forms in primates. Anthro- 

 poids have a tubular form, 

 whereas prosimians (except 

 tarsiers) have a ring form. 



But New World and 

 A egyptop ith ecus mo n keys , 

 specimens of which were 

 discovered in the Fayum 

 desert in Egypt, have ring- 

 shaped ectotympanics. 

 Does that imply the Fayum 

 anthropoids are not the 

 ancestors of modern an- 

 thropoids? If so, from 

 which primate fossils did 

 modern anthropoids arise? 

 The tubular form of the 

 ectotympanic seems to first 

 appear in early Miocene 

 dryopithecines, the earliest 

 species to resemble modern 

 apes. Are paleontologists 

 looking at a set (or sets) of 

 parallel evolutionary se- 

 quences between "ring an- 

 thropoids" and "tubular 

 anthropoids"? 

 Lyle Hubbard 

 Dallas, Oregon 



Russell Ciochon and Gregg 

 Gunnell propose a primate 

 family tree (on page 57) 

 that is more conjectural 

 than it needs to be, given 

 current evidence. Their 

 proposed link among 

 lemurs, galagos, adapoids, 

 amphipithecids, and 

 omomyids is not supported 

 by any shared, advanced 

 characteristics, whereas links 

 among omomyids, tarsiers, 

 and anthropoids are. 



The authors also confuse 

 time and morphology. 

 Evolution is about docu- 

 menting the morphological 

 changes across time from 

 primitive to more advanced 

 forms. A species' phyloge- 

 netic position is decided by 

 morphology, not time. If 



new 10-million-year-old 

 specimens of African Homo 

 erectus were found this 

 week, the evolutionary po- 

 sition of Homo erectus rela- 

 tive to modern humans 

 would remain the same, 

 because the morphology of 

 Homo erectus would not 

 change. Similarly, the mor- 

 phology of Eosimias marks 

 it as a primitive member of 

 the anthropoid lineage; its 

 age is immaterial. 

 Daniel L. Gebo 

 Northern Illinois University 

 DeKalb, Illinois 



Russell L. Ciochon and 

 Gregg F. Gunnell reply: 

 Chris Beard seems to have 

 missed the point of our ar- 

 ticle — that until skeletal ev- 

 idence of amphipithecids 

 was discovered, their dental 

 remains could be interpret- 

 ed in a variety of ways. 

 Now, however, skeletal ele- 

 ments are known that 

 clearly indicate they were 

 adapoids. Dental features 

 shared by amphipithecids 

 and anthropoids might well 

 be convergences, a point 

 we have discussed in detail 

 elsewhere. Mr. Beard ap- 

 parently cannot envision 

 the possibility that a short- 

 faced adapoid existed, but 

 we can. We predict that 

 when additional skeletal re- 

 mains of the amphipithe- 

 cids are uncovered, they 

 will show the same primi- 

 tive adapoid features. 



The ectotympanic (the 

 bone the ear drum is 

 stretched across) takes a va- 

 riety of shapes in primates, 

 including, as Lyle Hubbard 

 notes, a tubular and a ring 

 form. The distributions of 

 shapes suggest that a ring 

 fused into the outer wall of 



10 



NATURAL HISTORY May 2006 



