>(Yuri Kuchinsky) writes:
>These two plants, _ipomoea_ and _lagenaria_, are central in many
>debates about diffusion. Indeed, the validity of the hypothesis
>about human-assisted diffusion of the sweet potato across the
>Pacific is accepted by great many reputable botanists and
>archaeologists.

And as has been pointed out the validity of the natural dispersal
of sweet potato has also been accepted by many reputable botanists.

>(Let us assume here that the seeds _can_ travel that far in salt
>water and still remain fertile. This assumption may be valid for
>_lagenaria_. For _ipomoea_, no persuasive model of "auto-diffusion"
>has been suggested. Is someone finally going to mention "the African
>swallow" here, of the Monty Python fame?)

Your statement that there is no persuasive model of "auto-diffusion"
of Lagenaria Siceraria and Ipomoea Batatas is just incorrect (unless
of course you mean "to me, Yuri, there is no persuasive model...").

For Lagenaria siceraria [the bottle gourd], "Whitaker and Carter
demonstrated that gourds could float in sea water for at least 347
days - ample time to have crossed the Atlantic by floating - and that
the seeds still retain their viability.  In fact, these scientists
found that the seeds would still germinate after having remained in
these gourds for six years" (Heiser 1979:101).

And as Mr. Burglin has also posted for Ipomoea batatas, "Purseglove
(1968).. [showed]...the seeds are viable for more than 20 years, they
are hard and dormant unless scarified; they are impervious to salt
water; and they are not buoyant, but the capsule is." (Sauer 1993:41)

Modes of autodiffusion for both species have been presented, if they
were not persuasive then no botanists would even consider them.

Finally, while it is obviously ludicruous for an African swallow to
carry a coconut (the basis of the Monty Python skit) there is no reason
not to postulate birds as a dispersal mechanism for small seeds.  In
quotes below you will see that botanists regularly regard bird action
as one means of plant dispersal so you shouldn't just pooh pooh it away.

>Suppose the seeds did, somehow, arrive to new shores. First, the
>opponents of diffusion by humans would have to demonstrate that the
>plants in question can survive by themselves in the wild in the new
>area. This should be easy enough to do: prove that these plants
>exist now in the wilderness -- growing by themselves without human
>protection from encroaching jungle (highly unlikely, IMO). Have such
>evidence been available? Not to my knowledge.

Then read on and see that for both it has been shown that what they
require are disturbed environments, not necessarily human care.

>_If_ you find such
>back-up information, then you can further hypothesize that these
>former domesticates have been found in the wild and "re-
>domesticated" by natives. More reliance on chance
>
>For _lagenaria_ one possible scenario has been suggested: an African
>gourd has washed up on a beach in the Amazon delta area, was picked
>up by an inquiring native, and domesticated thereupon. Obviously,
>the chances of this happening don't seem very high, but such a
>possibility cannot be discounted offhand. Nevertheless, as
>agriculture was unknown in S America at that time, this would have
>been quite a feat! But a domestication could have been
>"involuntary", someone in these groups suggested. The seeds were
>thrown into a dump and grew... But this is still a "domestication"
>of sorts. So, our opponents wish to insist, the domestication of
>_lagenaria_ just happen to signify an independent invention of
>agriculture in the Americas. What an incredible coincidence!
>Lagenaria (that, on good evidence, was the first domesticated plant
>in Africa) ALSO became such a plant in the Americas -- but without
>any human contact! Wow!
>
>Again, what are the chances of a native FINDING a gourd on the
>beach? The chances of a gourd arriving at all are not that great to
>start with, but our opponents invite us to suppose that, on top of
>that remote chance, the natives would also patrol all the beaches
>all day long, so that they find it upon arrival! A Christmas present
>from Africa?

Your model that for Lagenaria siceraria to survive after a transoceanic
voyage it would need human action is just incorrect.  As you have
elsewhere noted, Heiser is not averse to accepting the possibility of
pre-16th  century Old/New World contacts, let's see what his model is:

"a large number of people believe that the gourd [Lagenaria siceraria]
must have floated across the ocean.  Many others, on the contrary, feel
that it must have been introduced by man.  To tally up the numbers who
hold one or the other of these views might be interesting, but it would
solve nothing."(p. 101-102)

"I do not think I have any preconceived ideas in regard to transoceanic
diffusion before Columbus.  In fact, I have sometimes been criticized
for straddling the fence." (p. 103-104)

pp. 105-110 Heiser summarizes Lathrap's arguments for why Lathrap
believes the gourd to be a human introduction from Africa to South
America.

"That a gourd soon disappears from a cultivated area, once cultivation
is abandoned, is probably not unlikely.  Gourds are dependant upon
disturbed areas...such disturbed areas today are usually created by man,
but natural disturbances such as river flooding, forest fires, earthquakes,
and landslides do occur without man's aid." (p. 113)

"Man has made it [Lagenaria siceraria] a domesticated plant, but even
so it does not require the pampering that many of our domesticates do.
In many places the plants are given no cultivation after the seeds are
started.  In this connection it is perhaps pertinent to mention that the
Indians of Virginia believed that it was unlucky to plant gourds, so they
simply scattered seeds on the ground to start new plantings." (p. 113)

"The botanist Henri Pittier collected a specimen, now in the United States
National Herbarium (4138), growing along a beach at Viento Frio in
Panama.  I am not claiming that this plant resulted from a transoceanic
voyage, only that it proves it will grow on a beach.  Moreover, I am not
sure it is necessary to prove this [although he just did], for strong
waves, perhaps the result of a hurricane, might carry gourds inland to a
suitable site for growth." (p. 115)

"the time has come for an alternative hypothesis [to Lathrap's].  Very
simply it is this - the gourd floated to America." (p. 114)

"Such a hypothesis of long-distance dispersal by natural means might
have caused raised eyebrows among past generations of botanists, who were
trying to explain all discontinuous distributions across oceans by means
of hypothetical land bridges or lost continentss.  Today, however, it is
widely accepted that there are many examples of long-distance dispersal
of plants by birds, wind, or water currents and subsequent establishment
in the New World." (p. 115)

"So I claim it is likely that a gourd, probably wild, became established
in the Americas after floating across the ocean." (p. 116)

So Heiser makes it clear that Lagenaria siceraria can survive without
man's aid - contrary to what you seem to be claiming above.

>To come back to the _ipomoea_. Has someone suggested a potato
>washing up on the beach in SE Asia? I hope not. That whole argument
>about a native finding the plant on the beach and domesticating it
>is non-existent for the potato (as opposed to a gourd). This is why
>the sweet potato is still the best candidate for human-assisted
>diffusion. _Ipomoea_ is always propagated through cuttings! It is
>never even grown from seeds by tribal peoples. Why? Because it is a
>highly domesticated plant in need of constant care, and it is not
>even clear that it _can_ grow from seeds in normal conditions.

It is actually clear that Ipomoea batatas CAN grow from seeds which
are naturally dispersed.   Athough Yen (1974) does tend to conclude
that humans are more likely means for its Polynesian origin, he does
cite (on pp. 235-239) a number of examples of its localized dispersal
and growth without the care of humans.  You are just incorrect when
you say that there isn't evidence that it can grow without the care
of humans.

>While opinion on the gourd is still rather divided, specialists in
>the field agree, on the whole, that the sweet potato was brought out
>of the Americas to Polynesia, and likely even to the Asian mainland
>-- by seafarers -- well before Columbus.
>
>Yuri.

So for both Ipomoea batatas and Lagenaria siceraria there is evidence
that their respective transoceanic dispersals could have been the
result of natural processes.  For each a possible autodispersal
mechanism has been proposed and for each it has been demonstrated that
they can propagate without human intervention.  So the question remains
open as to whether their dispersal was the result of human or natural
actions.  Without convincing supporting artifactual evidence of contact
I will continue to lean to the natural hypotheses.

Peter van Rossum
PMV100@PSU.EDU

Heiser, Charles
  1979 "The Gourd Book." Norman: Univ. of Oklahoma Press.

Sauer, Jonathan D.
  1993 "Historical Geography of Crop Plants: A Select Roster."
Boca Raton: CRC Press.

Yen, D.E.
  1974 "The Sweet Potato and Oceania: An Essay in Ethnobotany." Bernice
P. Bishop Museum Bulletin, no. 236. Honolulu: Bishop Museum Press.