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Anne Chao's 1984 paper positions its own method as a direct methodological
descendant rather than a fresh invention: "The method is similar to that
taken by Harris (1959). We first estimate En₀, the expected value of the
number of unobserved classes. Harris (1959) proved that for r = d(N), [bound
follows]." Harris's 1959 "Determining bounds on integrals with applications
to cataloging problems" (*Ann. Math. Statist.* 30, 521–548) supplies the
underlying asymptotic occupancy bound; Chao and, before her, Cobb & Harris
(1966) reused the same distribution-function approach for other statistical
problems before Chao applied it to the unseen-species count.

The paper also shows its own estimator, under a polynomial rather than
distribution-function approximation, collapses exactly onto a competing
estimator: "we obtain exactly the jackknife estimator given in (1). Thus this
approach also provides a justification of the use of the jackknife
estimator" — crediting Burnham & Overton's (1978, 1979) prior jackknife
method as a special case her more general method recovers. The 1984 paper is
therefore one point in an explicit lineage — Harris (1959) → Cobb & Harris
(1966) → Burnham & Overton (1978/1979) → Chao (1984) — not, as the
Good-Turing/Chao1 pairing sometimes reads informally, a second independent
route to the same object as [[claim-unseen-species-problem-has-dual-origin-ecology-and-cryptanalysis|Good and Turing's wartime derivation]].

> [!note] Seek's commentary:
> Every cluster this vault has built around the unseen has a convergence
> story — ecology and cryptanalysis reaching the same formula from opposite
> directions, paleobiology reinventing coverage-based subsampling under a
> different name. This is the other kind of story, and it's worth keeping
> distinct: not two strangers arriving at the same place, but one line of
> people handing a bound forward and each saying, plainly, whose shoulders
> they're standing on. Chao didn't have to cite Harris. She did, in the same
> paper that turns out to have picked up an uncredited addition somewhere
> after her — which makes her own citation discipline the more striking fact
> by contrast. — Seek