# Talk:1338: Land Mammals

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Is it mass or weight? --173.245.53.119 06:38, 5 March 2014 (UTC)

It says weight. Since most land animals live on the... land, there is not much difference. I suppose if a lot of aninimals lived near a prime pole vaulting location it could skew the results. 108.162.246.117 06:40, 5 March 2014 (UTC)
Ton is a unit of the quantity mass, not weight. Weight is a force and forces would be measured in newtons. Hence the comic is making a mistake. One that 99% of the people do. Mass would be correct since it is a more fundamental quantity and is usually what is meant when people talk about weight. 108.162.254.105 18:29, 9 March 2014 (UTC)

I'm really curious, what are the other, unlabeled groupings? Author's website 108.162.215.46 (talk) (please sign your comments with ~~~~)

```On page 186 of Smil's referenced book, there is a bar chart with the following values in millions of tons (*=not used in Randall's graphic):
elephants 0.8
horses 40
pigs 100
cattle 450
people 280
*whales 80
*all wild vertebrates 30
*all domesticated vertebrates 650
```
108.162.215.46 (talk) (please sign your comments with ~~~~)

I think that this graph is actually more illustrative of how much support humans need to maintain themselves (the amount of cattle is astonishing). lcarsos_a (talk) 07:58, 5 March 2014 (UTC)

need? I don't think we need so much cattle. It's just that most people prefer hamburgers and steaks to beans. So, how much we use to maintain ourselves would be better. (BTW, you don't count yourself as human?) -- Hkmaly (talk) 10:39, 5 March 2014 (UTC)
According to [1] there are 525 million dogs, assuming 20 kg as average weight, this should give 10 squares in the diagram. I can't find reliable numbers for cats, but there are more cats than dogs, but they don't weigh as much, so their total weight could be similar to that of the dogs. --108.162.254.160 08:42, 5 March 2014 (UTC)

The blob of 13 under the word Livestock may very well represent both dogs and cats. 108.162.215.46 (talk) (please sign your comments with ~~~~)

## Contents

### Layout of the blocks

Does anybody see a reason for the particular layout of the blocks? My first impression was a globe but obviously it doesn't correspond to any continents, etc. 108.162.254.66 08:44, 5 March 2014 (UTC)

I've been wondering myself... I do think it is a picture of something. My ideas so far: an eye, a fried egg, a cell. --Divad27182 (talk) 09:29, 5 March 2014 (UTC)
It may simply be something-like-a-circle of humans with the rest surrounding it. But it DOES look like a cell. -- Hkmaly (talk) 10:39, 5 March 2014 (UTC)
Could it be a sort of relationship diagram? It looks like we're in the centre, with the animals we have the closest relationships with — our pets and our food — nearest, and those we're less concerned with further away. Gidds (talk) 11:34, 5 March 2014 (UTC)
Yes, the overall layout is human-centric, but that doesn't explain the intentionally lumpy and asymmetric regions. It would have been easier to place the blocks in regular shapes (circular, rectangular or otherwise) but Randall chose to do it this way. Cell with a nucleus is a reasonable guess. - Frankie (talk) 14:00, 5 March 2014 (UTC)
I think it resembles a (low resolution) globe, with humanity representing the major continent Boxy (talk) 14:19, 5 March 2014 (UTC)
I think it shows the relationship of the title text (assuming we are part of land mammals): there are about 1.2K squares in total representing a factor of 1K:1 overall. Thus the shape (resembling bacterium) is explained, the incorporation of all mammals into the shape, and the potential central location of humans (assuming most bacteria lives in our gut). 108.162.219.31 16:09, 5 March 2014 (UTC)
I'm thinking the data points are placed using a polar coordinate system (although what the axis are I don't know, other than that being human gets you close to the center) combined with a mapping onto an x-y grid. Does that make any sense? --RenniePet (talk) 20:56, 5 March 2014 (UTC)
I think the layout is intended to show two legged mammals in the middle and four legged surrounding it. There are not sufficient six legged mammals to make yet another circle outside the four legged circle. Spongebog (talk) 16:47, 6 March 2014 (UTC)
You know of ANY six legged mammal? Any six-appendages vertebrate I know of is mythological creature (like pegasus or some dragons) or non-earth origin (like tree cats or Pandora-native). -- Hkmaly (talk) 10:58, 7 March 2014 (UTC)

### Identifying the groups

I would love to identify specific groups. The unlabelled animals come in groups, even the wild animals, even though only *one* of those groups (elephants for some reason) has been labelled. —TobyBartels (talk) 13:05, 5 March 2014 (UTC)

Reason for elephant label == "This is how much/little the whole population of the largest land mammals amass to."? (Actually, given the scarcity of elephants, I'm surprised it's a full block. I suspect something else that could have been labelledsuch as "rats" would be far more.) 141.101.99.7 14:07, 5 March 2014 (UTC)

Per the wikipeda page[2] on camels I expect that they are the blob of 3 gray squares. Mwiser (talk) Update: I hadn't seen the 1 billion kg == 1 million tons notation which has since appeared. I therefore added camels (and also donkeys) to the table below. Mwiser (talk)

Non SI units should just die already. 108.162.241.8 20:39, 5 March 2014 (UTC)

Is Randall's ton the metric tonne or the US short ton? -- 108.162.219.65 22:06, 5 March 2014 (UTC)
Considering that Randall is very aware of the SI confusion, I'm sure he would have made it clear if he where NOT using metric tonne - so I would say his tonne is 1,000 kg! Kynde (talk) 08:53, 6 March 2014 (UTC)

### Stab at the numbers

Land Mammal population in Billions Average Kilograms Total Kilograms in Billions xkcd value Notes
Humans 7.2 70 504 556 as of 2013
Cattle 1 1740 1740 1918 as of 2012
Pigs 1 350 350 386
Chickens 19 1 19 21 not mammals
Goats 0.865 46 39.7 as of 2008... src
Sheep 1 80 80 88
Elephants 0.000105670 5000 0.5 as of 2012 src
Horses 0.058372106 500 29 as of 2006 src
Rats 10 0.35 3.5 4 10B is a guess
Cats 0.6 5 3 3
Dogs 0.4 40 16
Seal 0.022 200 4.4 5 not a land mammal
Mole 6×1014 0.075 4.5×1013 Numbers are slightly exaggerated, but it would be nice to have those quantities
Krill  ?  ? 175-725 Wild species with largest biomass (not a land mammal)src
Camel 0.014 465 6.51 As of 2010 src
Donkey 0.04 160 6.4 As of 206 src mass src

108.162.241.8 16:19, 5 March 2014 (UTC)

### Talk about the table

uhh.... chickens aren't... mammals? (?) Brettpeirce (talk) 17:22, 5 March 2014 (UTC)

Apparently not. http://www.ask.com/question/are-chickens-mammals
--RenniePet (talk) 03:23, 6 March 2014 (UTC)
Where does these XKCD numbers come from? Cattle 1740? Humans 556? According to the comic there are 520 Cattle and 358 Humans (million ton). This table makes no sence in the XKCD number department. Appart from that it would be a great table to include in the comic... Kynde (talk) 08:52, 6 March 2014 (UTC)
Where does the average weight come from? As the human race is very young (26% below 15 years) and the cattle population has is changed very rapidly - thus there will also be many calves all the time - reducing the average weight far below that of an average adult animal ready to made in to beef... Kynde (talk) 09:55, 6 March 2014 (UTC)
Maybe the seal is considered a land mammal by Randal? Only wales are really not land mamals. The link to elephant population seems only to cover African elephants not Asian... Kynde (talk) 11:01, 6 March 2014 (UTC)
Does Randall consider cattle to be all the genus Bos? Waterbuffalo for example weigh about 400kg and wikipedia claims a world population of 130M. That would be 52 blocks. So, I'd assume that since there aren't any free blocks that large, that they are considered cattle. So, then Yaks and Wildebeests should be considered cattle as well, no? 108.162.215.36 22:06, 7 March 2014 (UTC)rbnm
sorry I meant Tribe Bovini not genus Bos 108.162.215.36rbnm

Rodentia? If the average rodent weighs something like 0.67kg, then 15B rodents would make up 13 squares. 0.67kg comes from the log average of the smallest and largest. If this includes rats (4B per the WHO) - is it reasonable that the rest of Rodentia includes 11B, 1-2 rodents per person on the Earth? That would include: squirrels, porcupines, beavers, guinea pigs, and hamsters; although guinea pigs might be considered pet/livestock (mmm... cuye!). 108.162.215.36 23:56, 7 March 2014 (UTC)rbnm

### Title Text

The title text mentions that bacteria outweigh humans by thousands (plural) to one. The notation 1000:1 used in the explanation is therefore not correct.

True - I did not spot that. I have corrected it to the same version as the title textKynde (talk) 19:15, 6 March 2014 (UTC)