I don't understand the use of "but" here. It seems to me that "and", rather than "but", should have been used. "It looks similar to x, and have much in common with x" sounds smooth, but it sounds odd if you used "but" here. I am not very sure.

What does "but" mean here?

Baum, who works at the University of Wisconsin–Madison, was looking at an archaeon: a type of microorganism best known for living in extreme environments, such as deep-ocean vents and acid lakes. Archaea can look similar to bacteria, but have about as much in common with them as they do with a banana. The one in the bioRxiv preprint had tentacle-like projections, making the cells look like meatballs with some strands of spaghetti attached.

Source: Nature The mysterious microbes that gave rise to complex life

  • 7
    Look at the “as much X as Y” construct as a single idea, and the “but” makes sense.
    – StephenS
    May 20 at 4:06
  • 9
    If you included "as they do with a banana" in bold as well (as it should have been) I think it would make more sense to you.
    – Kirk Woll
    May 20 at 20:47
  • I had real trouble with the question, because the headline does not make sense. Please edit and do not bury the comparison with a banana deep in the text. May 21 at 21:19
  • @Francis Davey: I've edited the title. But notice that it would make some members' comments look unnecessary.
    – NewPlanet
    May 22 at 2:39

The point of the sentence is that archaea don't have much in common with bacteria.
They have as much in common with bacteria as they do with a banana...

Archaea have almost nothing in common with bananas, and almost nothing more than that in common with bacteria.

About as much in the original sentence could be replaced with as little.

That is why "but" is used - it's a contrast between the similarity of appearance and the dissimilarity in other aspects.


If you use "and" in that sentence, it means that archaea and bacteria are similar. That's not the intent of the sentence. The author wants to say that they are not similar, and hence they've used the word "but" to mean

Archaea can look similar to bacteria, but they're not similar.

You can see this from the difference between the definition of but

used to introduce an added statement, usually something that is different from what you have said before.

and and

used to join two words, phrases, parts of sentences, or related statements together


The confusion here is not "A but B", it's misunderstanding the "as X as Y" construct, leading the querent to mistake what phrases are being joined by the conjunction (and therefore seeing it as an "and" connection rather than a "but" connection).

"as X as Y" is a standard comparative phrase (see this question as an example) and needs to be read as a whole. So the two phrases that are being connected here are:

  1. "Archaea can look similar to bacteria" , and
  2. "have about as much in common with [bacteria] as they do with a banana".

And the meaning of 2 is "nothing in common at all, except they're both organic", as Jack O'Flaherty makes clear.

Yes, if the phrase was "Archaea can look similar to bacteria, and they have much in common" (",but not this or this" would be the expected continuation, to explain the differences), that would make sense. But that's not the intent. The intent is "they look alike, but they really aren't", and to do that, the writer uses the "as X as Y" comparative in an ironic way, to emphasize how little alike they are.

Another example of this phrase would be "His sisters are about as alike as skyscrapers and submarines" (both of which do, in fact, have people and furniture in them, but...). Pushing harder for comedic purposes, Blackadder (a TV series) used this construction and a riff off the "two peas in a pod" idiom, saying "We're about as similar as two completely dissimilar things in a pod."

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