the middle-ear covering, 

 like the one in New World 

 monkeys, is primitive for 

 anthropoids. The same 

 configuration occurs in ad- 

 vanced Fayum anthropoids 

 such as Aegyptopithecus, 

 making them good candi- 

 dates for being identified 

 as the ancestors of all later- 

 occurring and more de- 

 rived anthropoids. 



Daniel L. Gebo is more 

 willing to accept the dubi- 

 ous evidence he and his 

 colleagues have presented 

 linking omomyids, tarsiers, 

 eosimiids, and anthropoids 

 than we are. Our figure de- 

 picts what is actually 

 known. As for confusing 

 time and morphology, the 

 only thing that is confused 

 is Mr. Gebo s interpretation 

 of our figure. His exagger- 



ated example of a 1( (-mil- 

 lion-year-old Homo erectus 

 reflects the flaw in his argu- 

 ment — at some point logic 

 must override parsimony. 



Signs of Life 



Neil deGrasse Tyson's arti- 

 cle, "Exoplanet Earth" 

 [2/06], reminded me of a 

 few questions I have had for 

 decades: What would atom- 

 ic explosions in the atmos- 

 phere look like to an ob- 

 server far from Earth? Could 

 they be seen from nearby 

 stars? If so, wouldn't a nu- 

 clear explosion on a small, 

 rocky, water-covered planet 

 be an unnatural event in the 

 universe and, thus, clearly a 

 signal of the presence of a 

 technological civilization? 

 John Marshall 

 Beai'erton, Oregon 



Neil deGrasse Tyson 

 REPLIES: Remarkably, an 

 asteroid slamming into our 

 atmosphere would be 

 largely indistinguishable 

 from the air blast of a large 

 nuclear bomb. Each repre- 

 sents an enormous and sin- 

 gular deposit of energy. So, 

 to an eavesdropping alien, 

 the simplest explanation 

 for mushroom clouds on a 

 small, rocky planet would 

 surely be asteroid im- 

 pacts — not the preposter- 

 ous idea that the planet 

 had evolved creatures stu- 

 pid enough to harness nu- 

 clear power for mutual ex- 

 termination. 



The famous 1908 

 Siberian air blast (the 

 "Tunguska event") was 

 caused by the explosion of 

 an asteroid the size of a 



fifteen-story building 

 when it hit Earth's atmos- 

 phere. In an instant, it 

 released the energy equiv- 

 alent of sixty atomic 

 bombs of the kind 

 ciropped on Hiroshima. 

 As for smaller asteroids, 

 about the size of houses, 

 the U.S. Strategic Com- 

 mand reports several 

 dozen of them burst in 

 the air per year, each re- 

 leasing the energy of a 

 single A-bomb. 



Natural History welcomes cor- 

 respondence from readers. Letters 

 should be sent via e-mail to 

 nhmag@naturalhistorymag 

 .com or by fax to 646-356- 

 65 1 1. All letters should include 

 a daytime telephone number, 

 and all letters may be edited for 

 length and clarity. 



Expedition to 

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Horn So/7 through some 

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 fjords. Only a small vessel like the Clipper 

 Adventurer can sail the "inside passage" 

 —the English Narrows— of Chile's fjords; 

 larger ships must remain mostly outside 

 in the open Pacific. 



November 8-12 2006 

 Aboard the 122-Passenger 

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