[Taxacom] Pop article on taxonomy's decline

Peter Stevens peter.stevens at mobot.org
Sun Jan 30 16:03:15 CST 2011


Actually, when it comes to memorization, it is not absolute numbers  
per se, but the ability to chunk things up into units of appropriate  
size, or use some other trick (such as putting numbers/objects/ideas  
in rooms, and taking a house/street tour) that matters.  If you look  
at Bentham and Hooker's "Genera plantarum" and just focus on  
categorical ranks, you will see great disparities in sizes of taxa,  
but if you analyse the whole three volumes, and you look at all the  
"informal" divisions that are there, you find that the size of the  
groupings is very close to the magic number - and this was Bentham's  
specific intent.

p.
On Jan 30, 2011, at 5:58 AM, Neal Evenhuis wrote:

> It also holds with the Australian/Oceanian Diptera catalog: 7.80  
> (15764 spp. in 2021 genera).
>
> -Neal
> ________________________________________
> From: taxacom-bounces at mailman.nhm.ku.edu [taxacom- 
> bounces at mailman.nhm.ku.edu] On Behalf Of Thomas Pape [TPape at snm.ku.dk]
> Sent: Sunday, January 30, 2011 1:43 AM
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Pop article on taxonomy's decline
>
>>>> So, either the vascular plants are much more speciose per genus  
>>>> than other organisms, or my average of 8 is a gross  
>>>> underestimate [...] it would be interesting to see some figures  
>>>> for other groups, particularly major insect groups ...
>
> The issue of 'how many species per genus' is perhaps more a  
> psychological or cognitive issue in so far as genera are man-made  
> constructs. Eight is (today) the number of bits in a byte. Eight is  
> the lucky number in many cultures. Even more compelling, perhaps,  
> is that the human mind on average has the capacity to operate  
> simultaneously with seven words, concepts, sounds or the like  
> (***Miller 1956). So, perhaps the human mind has an innate urge to  
> break up genera when they exceed that number?
> When Roger Crosskey (1980) edited the Afrotropical Diptera  
> catalogue, he made this interesting observation on the number of  
> species per genus:
> Afrotropical:   8.12 (16,318 spp. in 2,009 genera)
> Oriental:               8.51 (15,694 spp. in 1,876 genera)
> Nearctic:               8.18 (16,130 spp. in 1,971 genera)
> However, if calculated from what we currently have in Systema  
> Dipterorum (www.diptera.org), the figure is slightly above 13  
> species/genus.
> /Thomas Pape, Natural History Museum of Denmark
> ***Miller, G.A. (1956) The magical number seven, plus or minus two.  
> Psychological Review 63: 81-87.
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