2269: Phylogenetic Tree

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Phylogenetic Tree
And I was kicked out of my March Madness pool because I wouldn't shut up about the evidence for NBA/ABA endosymbiosis.
Title text: And I was kicked out of my March Madness pool because I wouldn't shut up about the evidence for NBA/ABA endosymbiosis.


In biology, phylogenetic trees are a way of showing evolutionary relationships between species. Each split in the tree represents a species that was the common ancestor of the two species beneath it, resulting in a bifurcating structure that can be followed all the way back to a single root - the most recent common ancestor of all species in the tree.

In sport, a tournament tree is a diagrammatic way of showing the progress of competitors in an elimination tournament. Each split in the tree represents the winner of a match between the two competitors beneath it. This too results in a bifurcating tree structure, which eventually terminates at a single root representing the champion of the tournament. Tournament brackets are a recurring theme at xkcd.

In this comic, Randall has taken advantage of the similarity between these two diagrams in order to prank his fellow biologists.

Each year in the United States, in March and early April, 68 National Collegiate Athletic Association (NCAA) Division I college basketball teams play in a single elimination postseason tournament to decide the national champion of college basketball. This tournament is colloquially known as March Madness. Associated with this tournament, it has become commonplace to guess the outcomes of each game, and predict who will win the tournament. A diagram illustrating the progress and elimination of teams through the tournament is called a bracket. Presumably Randall is referring to the men's college basketball tournament here, though there is a separate women's college basketball tournament that is also referred to as "March Madness".

Randall has replaced the trees in a biology paper with a basketball March Madness bracket, which is not related to biology. The 2019-20 NCAA college basketball regular season had not ended yet at the time of this comic's publication, so the partial bracket shown is a fictional bracket. Compared to a phylogenetic tree, the 'root' of a tournament tree is the final result (once known), rather than the common ancestor that was prior in time to all those that came after; the 'leaves' are all the initially hopeful competitors, rather than the latest extant (or unsucceeded extinct) organisms.

The title text shows the inverse of what the comic says: Apparently the March Madness bracket pool removed Randall after he tried to introduce biology-related evidence comparing the National Basketball Association (NBA) and American Basketball Association (ABA) to organisms and claiming the ABA is an endosymbiont living inside the NBA. An endosymbiont is an organism living inside another organism. In a way, this can be considered true of these two leagues, as the NBA and ABA merged in 1976 after which the ABA ceased to exist. 4 teams from the ABA, the Denver Nuggets, Indiana Pacers, Brooklyn Nets and San Antonio Spurs, continue to exist today as NBA teams. It is additionally humorous that Randall brings up the ABA/NBA merger in a March Madness bracket group, as March Madness is a college basketball tournament, as opposed to professional basketball played by the NBA and ABA.

A March Madness bracket was also the topic of 1819: Sweet 16.

Teams shown in the bracket[edit]

The bracket shows the Duke University basketball team winning the NCAA college basketball tournament. Strangely, it shows Gonzaga University linked only to explicitly non-Gonzaga branches, suddenly appearing out of the bottom section, which is not possible in a sports bracket context, but possible in biology if Gonzaga is an identified ancestral root with all descendant evolved species identified by a new term. In fact, the implied unchanged continuity of Duke from 'universal ancestor' to niche population sharing the world with all of its diverged and re-evolved outbranchings (rather than perhaps used as a term for a typically broad cladistic group of branches, such as Archaea) would be more curious - or just imply an inherent of available precision in the necessary paleobiological studies that classify the proposed UA and its descendency.

As of the publish date of this comic, all of the college basketball teams mentioned (except the University of Virginia) were ranked in the top 25 of the Associated Press poll. The University of Virginia was the 2019 national champion (winner of the tournament), so that may have been why they were mentioned.

Team name University Ranking Notes
Dayton University of Dayton #5 A private Roman Catholic research university in Dayton, Ohio. Dayton has appeared in 18 tournaments, most recently in 2017.
Duke Duke University #6 A private research university in Durham, North Carolina. Duke has appeared in 43 tournaments (most recently in 2019), and has won 5 national championships (most recently in 2015).
FSU Florida State University #8 A public research university in Tallahassee, Florida. Florida State has appeared in 17 tournaments, most recently in 2019.
Gonzaga Gonzaga University #2 A private Roman Catholic university in Spokane, Washington. Gonzaga has appeared in 22 tournaments, most recently in 2019.
Kansas University of Kansas #3 A public research university with its main campus in Lawrence, Kansas. Kansas has appeared in 48 tournaments (most recently in 2019), and has won 3 national championships (most recently in 2008).
Louisville University of Louisville #11 A public research university in Louisville, Kentucky. Louisville has appeared in 39[note 1] tournaments (most recently in 2019), and has won 2[note 1] national championships (most recently in 1986).
UVA University of Virginia Unranked A public research university in Charlottesville, Virginia. Virginia has appeared in 23 tournaments (most recently in 2019), and won a national championship in 2019.


[A circular phylogenetic tree is shown, with various parts of the tree colored red, green, blue, and black. Text is written on the root of the tree and the first few branches, getting smaller until it becomes unreadable. The visible text is:]
Duke Gonzaga
Louisville Duke UVA FSU
Dayton UVA Kansas FSU
[Caption below the panel:]
I was kicked off the biology project after I secretly replaced all the phylogenetic trees in our new paper with March Madness brackets.


  1. 1.0 1.1 Louisville vacated its tournament results from 2011-15, including its 2013 national championship, due to NCAA violations.

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Because of timezones this comic was released on Sunday in some areas 07:21, 17 February 2020 (UTC)

Well, it's always either that or Tuesday in some areas, right? However, yes, this again was up quite early. But the exact upload times seem to fluctuate heavily all the time. --Lupo (talk) 07:40, 17 February 2020 (UTC)

I don't know much about basketball (only heard about march Madness here/xkcd and on HIMYM before), but where is Gonzaga coming from? shouldn't it be either UVA, Kansas or FSU? or is it a different name for one of those 3 teams? Also: Do we need a march madness category? maybe as a subcategory of bracket tournaments? It seems to be quite reocurring. --Lupo (talk) 07:43, 17 February 2020 (UTC)

Gonzaga is on here as a joke. In 2019, late night host Jimmy Kimmel humorously refused to believe that they were a real college from the start of the tournament. They lost in their division finals. 16:01, 17 February 2020 (UTC)
While you are correct, I think the question is how they show up in the tree without being shown on any of the lower branches. Since this tree is about genetics, my guess is it's supposed to be a mutation that just appears out of nowhere. Gonzaga has had a few good years in the past, most notably this detail from Wikipedia: "Gonzaga advanced to the Elite 8 of the 2015 NCAA tournament, losing to eventual national champion and No. 1 ranked Duke." I suspect it's no coincidence that they lose to Duke in this tree! Ianrbibtitlht (talk) 16:25, 17 February 2020 (UTC)

Could someone explain what a "March Madness Bracket" is? It appears to be something to do with American college basketball, but why does it have the same structure as a phylogenetic tree? What does the word 'Bracket' mean here? (talk) 07:48, 17 February 2020 (please sign your comments with ~~~~)

https://en.wikipedia.org/wiki/Bracket_(tournament) 07:51, 17 February 2020 (UTC)
Seconded. The explanation as it stands assumes that the reader is from the USA and understands American sports. Neither of these is true for me. Can we please have concise one-line explanations of:
  • what sport?
  • what teams?
  • what a bracket is?
  • what tournament this refers to?

I was a biologist; the science part is clear to me. It needs an explanation akin to that about phylogeny, for non-sports-followers and non-US-sports followers. Lproven (talk) 09:02, 17 February 2020 (UTC)

Getting better! Terms now undefined: "NCAA", "ABA", "NBA", "Division 1", "single elimination", "bracket pool", "college basketball". Lproven (talk) 11:05, 17 February 2020 (UTC)
NCAA = National Collegiate Athletic Association, but it doesn't cover all colleges -- just the bigger ones. NBA national Basketball Association, the (main?) pro basketball grouping of mens' teams (as opposed to the WNBA). ABA is _probably_ the American Basketball Association, of which I know nothing (but guessing by analogy with NBC/ABC television networks; National/American Broadcasting Company. And college basketball is, well, basketball played by college teams. For the rest of it, I'm out of my league. (talk) 06:41, 17 February 2020 (please sign your comments with ~~~~)
From what I understand, the NCAA categorize teams into divisions, with Division 1 being the highest. "Single elimination" is a type of tournament bracket where once you lose a match, you're done. A bracket pool is where people get together and each makes a prediction of the bracket. Whoever is closest to what actually happened wins. The ABA is the American Basketball Association. (talk) 09:02, 17 February 2020 (please sign your comments with ~~~~)
Well, to be fair, "bracket" is a rather generic sports concept, it isn't American, it should be worldwide, I believe it's used in Olympics and anywhere else teams or athletes must face each other two at a time where there's more than 2 trying to win the top spot. Team sports and combative sports mostly, sports like tennis too. In such 1-on-1 sports, if there are for example 8 competitors (whether they be full teams or single athletes), #1 will play #2, 3 against 4, 5 & 6, 7 & 8. Let's say all the lowest / odd numbers win, that means all the even numbers are eliminated from the competition, and in the next round (4 left means it's the semifinals), 1 faces 3 and 5 faces 6. Then the winners of these two matches/whatever will face each other in the finals, to try to win the entire competition. In an Olympic event, perhaps USA faces Canada and England faces France, then Canada and England win their matches and as such proceed to face each other for the gold (the loser of that match getting silver, and a separate sub-bracket would determine bronze, in this case I guess a match between USA and France).
This bracket is a little muddled (who did Louisville play? Where did Gonzaga come from?), but presuming Louisville won, they'd move on to face Duke, who won THAT, who then won against Gonzaga to win the whole thing. A bracket like this is just the visual representation of the tournament structure, to clearly see how the tournament progresses. It's funny, I'm not a sports guy, so I'm more suited to the science angle, but actually as an Olympic wrestling official, the guy in charge of filling out said brackets, in this case I understand the bracket stuff better, LOL! If you look up one of the comics with a completed bracket, you can better see how it plays out. You can probably just Google "xkcd bracket", LOL! NiceGuy1 (talk) 05:12, 22 February 2020 (UTC)
"Well, to be fair, "bracket" is a rather generic sports concept, it isn't American" - I think it isn't (or wasn't) a common term here in the Leftpondian Anglosphere. The term "elimination ..." or "knockout stages" are more common, though may apply also to pre-'bracket' intra-group games where (e.g. in football World Cup) four teams per group play six all-against-all-exactly-once games to pre-rank where to enter the tree-like elimination round at what these days is called the "round of sixteen", to then progress to each next lower round-of-(2ⁿ), although they already have the established name of ("quarter-"|"semi-"|"")final, which semantically become a superset over mere 'elimination' - and isn't even technically true where the non-finalists that emerge from the semis also get back to play off for (nominal) 3rd/4th places. In the FA Cup (competition for English+Welsh footbll clubs, it is described in terms of "Rounds" with Qualifying and Preliminary rounds (numbered) to whittle down the lower-tier clubs prior to inserting various intermediate and higher league teams (pre-qualified by dint of their league placement) into the First and Second Rounds (randomised pairings, from those inserted or earning their places) until the Third Round where all the top clubs given a bye until now (and all that survived earlier culling, including bottom-rung clubs that are potential "giant killers") contend in randomised pairings to reach the Fourth Round, Fifth Round, then Quarter-/Semi-/... Finals. Though maybe (re)imported sports (base/basketball, icehockey e.g.) could have brung us 'bracket' as terms, even if they were never really used in more homely equivalents (e.g. in rounders, netball, field-hockey), so far as I know. 16:38, 24 February 2020 (UTC)
Ah, there we go. I figure the basic concept must exist if not the terminology. Yes, "Elimination" is used here too (well, I'm Canadian, but we share such concepts). Used here is a Single Elimination Bracket, meaning that losing once puts the team/athlete out of the tournament. In wrestling we use a Double Elimination Bracket, once somebody loses they enter a secondary bracket to fight for 3rd, a second loss kicks them out of the tournament. "Bracket" is mostly referring to the visual representation of such a tournament structure. NiceGuy1 (talk) 03:50, 14 March 2020 (UTC)

The three prominent "Duke"s in the center of the chart, made me look for the logical continuation "of Earl." I didn't see it... :( (talk) 06:41, 17 February 2020 (please sign your comments with ~~~~)

That would be a reference to the 60's song Duke of Earl. It has a refrain "duke, duke, duke of earl..." SDSpivey (talk) 17:09, 17 February 2020 (UTC)
As a kid I thought it was "Ducca Girl", LOL! NiceGuy1 (talk) 05:12, 22 February 2020 (UTC)
Likewise. Also, duck fuke. (talk) 07:52, 17 February 2020 (please sign your comments with ~~~~)

SO is the displayed bracket last seasons? a prediction for this season? completely random? Are they even real universities? Or is Randall embedding more jokes? What is Basketball? why do universities play it? why do we care? It is only February - why are we discussing March? Mind you May Week is in June and the Octoberfest in September so March Madness could be in February for all I know? Arachrah (talk) 16:59, 17 February 2020 (UTC)

I'm operating under the presumption that the teams are random, being unfamiliar with the sport myself (random except that Duke is nice and short and easy to fit, LOL!). Except that the explanation mentions one team as being there as an inside joke. And as far as I know, March Madness IS in March, what's in February is probably the lead up, the games that determine who will be playing in March Madness, as well as fans filling out prediction brackets to predict (and bet on) how it will turn out. NiceGuy1 (talk) 03:50, 14 March 2020 (UTC)

And what is with the colours?

  • All the universities mentioned (at least, those whose names are legible) are real universities: Duke University, Gonzaga University, University of Louisville, University of Dayton, University of Virginia ("UVA"), University of Kansas, Florida State University ("FSU"). Most of them are ranked highly in the current basketball rankings (published by the Associated Press and compiled from a weekly poll of sportswriters) -- Duke #6, Gonzaga #2, Louisville #11, Dayton #5, Kansas #3, Florida State #8. (These are rankings of how well the basketball teams are playing in the current season.) Virginia isn't doing as well this season, but they did win the national championship last season. It is reasonable to predict that all seven of the universities mentioned will be selected to play in the tournament this year (about 350 schools are eligible, and 68 of them are selected). Since "March Madness" (the championship tournament) is the culmination of the entire season, basketball fans start caring about March Madness before the month of March starts. (This year the tournament begins on March 17 and ends on April 6.) This tree isn't formatted properly to be comprehensible as an actual prediction of the tournament. -- 18:45, 17 February 2020 (UTC)
  • ((In response to: What is it with the colours...)) In the Biological sense, colours indicate the direct 'lineage' from the common ancestor (or an offshoot from that line) to a given end-creature (or swathes as a whole family/clade/whatever branch). In the Bracketting sense, it would show the route to the final (or as far as they got) of a competitor or a group of competitors. I'm not sure which it's 'intended' to be, but I'm sure it's a common phylogenetic tree convention, outside of this peculiar mashup.
Incidentally, I misread the comic at first as mentioning 'Duke Gonzago', as per the lines from Hamlet: "The Mousetrap. Marry, how? Tropically. This play is the image of a murder done in Vienna. Gonzago is the duke’s name, his wife Baptista. You shall see anon. 'Tis a knavish piece of work, but what o' that? Your majesty and we that have free souls, it touches us not. Let the galled jade wince, our withers are unwrung." 18:54, 17 February 2020 (UTC)