ADAPTIVE RADIATIONS, BUSHY EVOLUTIONARY TREES,
AND RELICT HOMINOIDS
Jeff Meldrum*
Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007
*Correspondence to: Jeff Meldrum, Dept. Biol. Sci., Idaho State University, 921 S 8th Ave., Stop 8007, Pocatello,
ID 83209-8007. email: meldd@isu.edu.
[Reprinted by written permission of the author: I shall append some comments in a followup article]
Recent developments in paleoanthropology
have promoted a shift in attitude toward the
question of relict hominoids. Over a half
century ago, interpretations of the hominin
fossil record were markedly different.
Deriving from the influential evolutionary
concept of competitive exclusion (Gauss,
1934), as applied to human evolution (Mayr,
1950), it was deemed that only one species
could occupy the hominin niche at any given
point in time. From this emerged the Single
Species Hypothesis (Wolpoff, 1971). This
hominin niche was associated with adaptations
for habitual bipedalism, reduced canines, tool
use, and culture. The latter was thought
perhaps most significant, because with culture
and the plasticity of learning, a species could
conceivably broaden its niche space, further
reducing the potential for sharing the
landscape with other hominins (but see
Winterhalder, 1981).
In 1976, Washburn and Ciochon challenged
the reach of the hypothesis and opined that it
was not until the emergence of Homo erectus
that one species became so successful that all
others were eliminated. They allowed that the
preceding more “ape-like hominins,” i.e. the
australopithecines, offered a radiation of
contemporary coexisting species (see Lewin &
Foley, 2004).
Shortly thereafter, the hypothesis further
retreated when it was recognized that African
Homo erectus (now H. ergaster), a large-
brained human ancestor, had coexisted with
Australopithecus (Paranthropus) bosei, a
parallel lineage of small-brained facially
robust hominins that presumably eventually
went extinct (Leakey & Walker, 1976). These
species display the expected ecological
reaction to a sympatric competitor, i.e. niche
partitioning, involving diet, micro-habitat
divergence, and possibly also temporal
differentiation of resource use (Winterhalder,
1981). Stephen J. Gould (1976) made a
prediction in his popular column in Natural
History, stating: “We know about three
coexisting branches of the human bush [Homo
habilis, Homo erectus, and Australopithecus
bosei]. I will be surprised if twice as many
more are not discovered before the end of the
century.”
Indeed, mounting discoveries accumulating
at a steady pace, reveal dozens of hominin
species spanning a seven million year period
(see Tattersall, 1996, but see White, 2009).
The hominin phylogentic tree becomes
increasingly bushy with each additional
species. This proliferation of species is not
merely an artifact of taxonomic “splitters” vs.
“lumpers.” Martin (1990) has estimated that a
mere 3% of past taxonomic diversity in
primate paleocommunities has been
recognized and documented in the fossil
record. Assuming the same holds true for
hominins, and taking a conservative tally of a
dozen extinct hominin species, according to
Martin’s estimate there could conceivably be
400 species of hominin as yet unknown.
Given the particulars of the inferred natural
history of large-bodied primates, and
especially the tendencies for generalized
behavioral ecology of hominins, such a high
figure for hominin diversity seems rather
unlikely (Arcadi, 2006). It emphasizes
however, that the currently known fossil
record likely underestimates past diversity.
The perennial discovery of new hominin
species attests to that expectation.
In addition to this growing appreciation of
the bushiness of the hominin tree, there are
revelations of the ever more recent persistence
of a number of the branches or lineages within
the tree. One of the most surprising
discoveries was the enigmatic “Hobbit” or
Homo floresiensis. This diminutive hominin
unearthed on the Indonesian island of Flores
has been dated to as recent as a mere 18 ka
(Brown et al., 2004). The recognition of this
startling species even prompted the editor of
Nature to point out that since Homo
floresiensis survived until so very recent, it
was now more likely that stories of other so-
called mythical, human-like creatures, such as
the yeti are founded on grains of truth (Gee,
2004). He went on to acknowledge the
possibility that the taxonomic and adaptive
diversity of hominins was always high, has
remained high until very recently, and might
not be entirely extinguished. This was a
notable concession reflecting a changing
attitude, although one generally not so openly
displayed.
The justification of the attribution of the
“Hobbit” to the genus Homo has been
questioned due to its small brain-size and
primitive aspects of its skeleton (Meldrum,
2004). Recent studies of wrist and foot bones
reveal primitive anatomies reminiscent of H.
habilis or Australopithecus, again leading
some to propose a pre-erectus African origin
for the species (Tocheri et al., 2007; Jungers et
al., 2009; Morwood and Jungers, 2009). This
raises even more questions over hypotheses
about the origins of H. floresiensis and its
arrival on the Indonesian island of Flores.
Australopithecines are presently only known
from Africa. Did a late australopithecine/ early
Homo disperse across Asia without leaving
any record of its passage? This is certainly
under serious discussion.
Another hominin potentially exhibiting a
more recent persistence then previously
recognized is Asian Homo erectus. Dating of
Homo erectus sites at the extreme of its range
in Southeast Asia has produced ages of 30-50
ka, suggesting possible contemporaneity with
modern H. sapiens arriving in the region
(Swisher et al., 1996). These younger dates
were seemingly contradicted by a later study;
however the older dates could be attributed to
reworked sediments at the site (Indriati et al.,
2011). Should the younger dates be
substantiated, this would prove a hominin
example of relative biogeographic isolation
and survival that parallels the persistence of
the last Neanderthals.
The discovery of the Denisova hominins
added another branch to the bush (Krause et
al., 2010). The fragmentary fossils date to
only 30 ka and were recovered from a cave
site in southern Siberia, in the Altai Mountains
near the Mongolian border. The completed
sequence of the Denisova hominin genome
established this species as distinct from
modern humans and Neanderthals (Reich et
al., 2010). The remains include remarkably
robust teeth and toe bones (Mednikova, 2011;
Reich et al., 2010). The tooth, if correctly
identified as a third molar, is as large as that of
an australopithecine. Green, one of the lead
researchers contemplated, "…you have to
wonder if there were other populations that
remain to be discovered.”
That Neanderthals and modern Homo
sapiens coexisted on the European continent
for tens of thousands of years has long been
recognized. During this extensive period of
overlap they remained separate and distinct
populations. The sequencing of the
Neanderthal genome has revealed minimal
introgression between the species (Green et
al., 2010; Currat and Excoffier, 2011). While
much press has been directed to this limited,
even trivial, gene flow, of even greater
implication is the flip-side to this observation
– that such genetically similar species
remained almost entirely distinct in spite of
millennia of contact.
A new cave site in the Altai Mountains has
produced additional Neanderthal fossils, at the
most easterly known extent of their range,
with preliminary dates of only 10-20 ka
(Reich, personal communication). This is less
than half the previous latest occurrence for
Neanderthals previously documented – 28 ka,
possibly as young as 24 ka (Delson and
Harvati, 2006). The geographic range for
Neanderthals may has increased in another
direction as well, with archeological evidence
suggesting they occupied the subarctic
northern extent of the Ural Mountains in
Russia, some 33 ka (Slimak et al., 2011). Only
the recovery of skeletal remains will confirm
this site as Neanderthal. The possibility of
Neanderthal persistence into the present has
been examined in the scientific literature by
Porshnev (1974), Bayanov and Bourtsev
(1976) and Shackley (1982).
Homo heidlebergensis (sometimes referred
to as archaic Homo sapiens) were large and
robust pre-modern hominins considered the
common immediate antecedents of modern
humans and Neanderthals. Some researchers
have portrayed them as “giants” dubbing them
“Goliath” in the popular literature
(Kappleman, 1997). Lee Berger suggested that
Homo heidlebergensis populations routinely
produced 7 foot tall individuals and
reconstructed them accordingly with Steve
Churchill for a National Geographic
documentary “Searching for the Ultimate
Survivor.” While middle Pleistocene hominins
were large, the Goliath moniker is an
exaggeration (see Ruff et al, 1997). Whether
Homo heidlebergensis’ range encompassed
eastern Asia is debated (Lu et al., 2011).
However, a specimen of pre-modern hominin
recovered from the site of Lishu, on display at
Peking University, has a preliminary date of
12-20 ka (Lu, personal communication).
Therefore, an observer of the Asian landscape
of only 20 ka could potentially encounter any
of a half dozen hominin species coexisting
there.
The implication of the recognized bushy
hominin tree was a major theme developed in
a Nova documentary series “Becoming
Human.” The final episode, which introduced
modern humans, was titled “Last Human
Standing: Many human species once shared
the globe. Why do we alone remain?”
Introductory remarks addressed the singular
circumstance of Homo sapiens’ solitary
inheritance of the world. The producers’
explanation for this situation echoed the
earlier pronouncement of Washburn and
Ciochon (1976) on the supremacy of Homo
erectus, by suggesting that in this case, Homo
sapiens were so successful that all other
hominins were eliminated from the scene.
This assertion may prove as unfounded for
Homo sapiens as it was for Homo erectus a
quarter century earlier. What was not
considered was the implication of the question
“Why do we alone remain?” — that is, why
would the present be the exception to the rule
that has apparently prevailed throughout
hominin history?
The fossil record of apes has likewise grown
into a very bushy tree. A remarkable
taxonomic and adaptive diversity of ape
species is unfolding, with nearly 100 extinct
species throughout the Miocene and Pliocene
(Begun, 2003; Cameron, 2004). We find apes
associated not only with evergreen tropical
forests but also with swamps, grassland
savannas, seasonal woodlands, and subtropical
to even temperate habitats not usually
considered associated with preconceptions of
ape lifeways. We find a diversity of dietary
and correlated dental adaptations, with
Eurasian hominids displaying enamel molar
thickness and canine reduction rivaling even
the most extreme morphologies of later
African hominins, such as the robust
australopithecines. We learn that the derived
ape form of locomotion, i.e., forelimb
suspension, must have evolved independently
in the Dryopithecinae, the modern African
apes, and a third time in Pongo — a powerful
example of parallelism to consider when
contemplating the multiple evolutions and
derivations of bipedalism. And yet even this
broadened perspective is inherently biased,
since representation in the fossil record is
skewed toward those habitats most conducive
to fossilization and those strata subsequently
uplifted and exposed to funded explorations.
There is a notable gap in the fossil record of
apes for the past 5 million years. The extant
great apes are themselves merely relict species
in tropical forest refugia, poised on the brink
of extinction. Virtually no immediate fossil
antecedents of the African apes are known,
with the exception of three isolated teeth of a
fossil chimpanzee 500 ka (McBrearty and
Jablonski, 2005). Sparse dental remains of
orangutan-like species are found throughout
the Pleistocene of mainland southeast Asia
(Zhao et al., 2009). The extant orangutan is
now restricted to the islands of Borneo and
Sumatra.
Few additional species emerge from the gap.
An Asian “mystery ape” has been suggested
as a newly recognized member of the mid-
Pleistocene Stegedon-Ailuropoda fauna
(Ciochon, 2009). However this may be less
mysterious than proposed and instead be a late
survival of Lufengpithecus, or a closely related
descendant form (Etler et al., 2001; Etler,
2009).
The only other ape currently recognized in
the Asian Stegedon-Ailuropoda fauna is
Gigantopithecus. This massive ape has been
referred to as the “fifth great ape” because it
had been the only species, other than those
now extant, recognized to have persisted well
into the Pleistocene, until 250-300 ka
(Cameron, 2004; Rink et al., 2008). The very
real potential for the persistence of
Gigantopithecus into the recent has been
acknowledged by past researchers such as
John Napier (1973), who observed, “It is
possible that these creatures, thought by
anthropologists to be long extinct, survived in
refuge areas such as some of the deep forested
river gorges of the Himalayan range until
relatively recent times. The absence of a fossil
record is not necessarily evidence of
extinction.”
As recently as 1998, Chris Stringer
acknowledged that the yeti legend might not
be so far-fetched as often presumed, and may
indeed have been inspired by surviving
populations of Gigantopithecus. He allows
that the giant ape may survive today in the
dense forests of Southeast Asia. Stringer
recognized that it would be wrong to assume
that Gigantopithecus-like creatures could not
survive to the present day without being
discovered. “It could have survived until the
appearance of modern humans 50,000 years
ago, and it is at least possible that it is still
living as a very rare creature in remote forest
areas,” Stringer contemplated. On this matter,
David Begun noted, “There is no reason that
such a beast could not persist today. After all
we know from the sub-fossil record that
gorilla-size lemurs lived on the island of
Madagascar until they were driven to
extinction by humans only 1,000 years ago”
(Begun, 2003).
There are numerous isolated specimens that
are suggestive of as yet unrecognized species.
We have likely only begun to scratch the
surface. Is the five million year gap in the ape
record actually the demise of this radiation?
Obviously the progenitors of the extant great
apes bridge the gap, although we have very
little to show for it. As for extant species —
the Bili (or Bondo) ape is remindful that the
discovery of the mountain gorilla in 1902
could well be repeated. In this instance,
genetic testing determined that the Bili ape is
a known subspecies of chimpanzee, Pan
troglodytes schweinfurthii, although a
population that is exceptionally large and
displays a unique culture with many habits
similar to those of gorillas (Hicks, in press).
Certainly it is possible that Homo sapiens is
indeed the last hominin standing; likewise,
that gorillas, chimps, bonobos and orangutans
are the last apes standing, or hanging as the
case may be. Extinction happens. But if we
are to learn from history, and recognize the
implications of the growing bushiness of the
hominoid tree, combined with the recent
persistence of several of its branches, then the
possibility of relict hominoids should not be
dismissed out-of-hand, particularly when
evidence – suggestive at least, if not yet
definitive – accumulates to that end.
Could a relict pre-modern hominin, e.g.
Homo neandertalensis, or Homo denisova, be
the explanation for the Russian almas? Could
a relict ape, e.g. Lufungpithecus, be the
explanation for the yeti of the subtropical
forests of the Himalayas? Could a relict
australopithecine be the explanation for the
orang pendek in southeast Asia? Could
Gigantopithecus, or some hominin, e.g.
Paranthropus, be the explanation for the
Chinese yeren, or the North American
sasquatch? In the context described above,
these are legitimate and timely questions
worthy of the serious consideration of the
anthropological community. Thus the birth of
the RHI.
LITERATURE CITED
Arcadi AC (2006) Species resilience in Pleistocene
hominids that traveled far and ate widely: An analogy
to wolf-like canids. J Hum Evol 51:383-394.
Bayanov D, Bourtsev I (1976) On Neanderthal vs.
Paranthropus. Current Anthropology 17(2):312-318.
Begun DR (2003) Planet of the apes. Scientific
American 289(2):74-83.
Berger. http://www.thenakedscientists.com/HTML/
content /interviews/interview/833/.
Brown P, Sutikna T, Morwood M., Soejono RP,
Jatmiko, Wayhu Saptomo E and Rokus Awe Due
(2004). A new small-bodied hominin from the Late
Pleistocene of Flores, Indonesin. Nature 431 (7012):
1055–106.
Cameron DW (2004) Hominid Adaptations and
Extinctions. Sydney: University of New South Wales
Press.
Ciochon RL (2009) The mystery ape of Pleistocene
Asia. Nature 459:910:911.
Currat M and Excoffier L (2011) Strong reproductive
isolation between humans and Neanderthals inferred
from observed patterns of introgression. PNAS
108(37): 15129-15134.
Delson E and Harvati K (2006) Paleoanthropology:
Return of the last Neanderthal. Nature 443:762-763.
Etler D (2009) Mystery ape: Other fossils suggest it’s
no mystery at all. Nature 460:684.
Etler DA, Crummett TL, Wolpoff MH (2001).
Longgupo: Early Homo colonizer or Late Pliocene
Lufengpithecus survivor in South China? Hum Evol
16:1-12.
Gee H (2004) Flores, God and Cryptozoology. Nature
431: 1055-1061.
Gould SJ (1976) Ladders, bushes, and human evolution.
Natural History 85(4):24-31.
Green, RE, Krause J, A. W. Briggs AW et al. (2010) A
draft sequence of the Neandertal genome. Science
328(5979):710–722.
Green. http://www.physorg.com/news/2010-12-fossil-
finger-bone-yields-genome.html.
Hicks TC (in press). Encounters with Bili chimpanzees
in the undisturbed Gangu Forest. In Among African
apes: Stories and photos from the field. MM.
Robbins and C Boesch (eds.) Berkeley: University of
California Press.
Indriati E, Swisher CC III, Lepre C, Quinn RL,
Suriyanto RA, et al. 2011. The age of the 20 meter
Solo River Terrace, Java, Indonesia and the survival
of Homo erectus in Asia. PLoS ONE 6: e21562
Kappelman J (1997). They might be giants. Nature
387:126-127.
Leakey REF and Walker AC (1976) Australopithecus,
Homo erectus and the single species hypothesis
Nature 261:572-574.
Lu Z, Meldrum DJ, Huang Y, He J, Sarmiento EE
(2011) Pedal skeleton of the Jinniushan hominin
from the Middle Pleistocene of China. Homo 62:389-
401.
Martin RD (1990) Primate Origins and Evolution: A
Phylogenetic Reconstruction. Princeton, NJ:
Princeton University Press.
McBrearty S, Jablonski NG (2005) First fossil
chimpanzee. Nature 437:105–108.
Mednikova (2011) A proximal pedal phalanx of a
paleolithic hominin from the denisova Cave, Altai.
Archaeology, Ethnology and Anthropology of
Eurasia 39(1):129-138.
Meldrum DJ (2004) A new small-bodied hominin from
the Late Pleistocene of Flores, Indonesia. Brown P,
SutiknaT, Morwood MJ, Soejono RP, Jatmiko, E.
Wayhu Saptomo E & Due RA. Nature 431:1055-
1061; Flores, God and Crytozoology. Gee H (2004)
www.nature.com/news/2004/041025/full/041025-
2.html. Journal of Scientific Exploration 18:725-728.
Morwood MJ, Jungers WL (2009) Conclusions:
implications of the Liang Bua excavations for
hominin evolution and biogeography. J. Hum. Evol.
57: 640–48.
Napier J (1973) Bigfoot: The Yeti ans Sasquatch in
Myth and Reality. New York: EP Dutton & Co.
Porshnev B (1974) The Troglodytidae and the
Hominidae in the taxonomy and evolution of higher
primates. Current Anthropology 15(4):449-450.
Reich D, Green RE, Kircher M, Krause J, Patterson N,
Durand EY, Viola B, Briggs AW, Stenzel U, Johnson
PLF, Maricic T, Good JM, Marques-Bonet T, Alkan
C, Fu Q, Mallick S, Li H, Meyer M, Eichler EE,
Stoneking M, Richards M, Talamo S, Shunkov MV,
Derevianko AP, Hublin JJ, Kelso J, Slatkin M, Pääbo
S (2010) Genetic history of an archaic hominin group
from Denisova Cave in Siberia. Nature 468: 1053–
1060.
Rink WJ, Wei W, Bekken D, Jones HL (2008).
Geochronology of Ailuropoda-Stegodon fauna and
Gigantopithecus in Guangxi Province, southern
China. Quaternary Research 69, 377–87.
Ruff CB, Trinkaus E, Holliday TW. 1997. Body mass
and encephalization in Pleistocene Homo. Nature
387:173-176.
Shackley M (1982) The Case for Neanderthal Survival:
Fact, Fiction or Faction? Antiquity, 56(216):31-41.
Slimak L, Svendsen JI, Mangerud J, H, Heggen HP,
Brugère A, Yuryevich PP (2011) Late Mousterian
Persistence near the Arctic Circle. Science 332
(6031):841-845.
Swisher, CC III, RinkWJ, Antón SC, Schwarcz HP,
Curtis GH, Suprijo A, Widiasmoro (1996) Latest
Homo erectus of Java: Potential Contemporaneity
with Homo sapiens in Southeast Asia. Science 274:
1870-1874.
Tattersall I (1996) The Fossil Trail. New York: Oxford
University Press
Winterhalder B (1981) Hominid paleoecology and
competitive exclusion: limits to similarity, niche
differentiation and the effects of cultural behavior.
Yearbook of Physical Anthropology 24:101–121.
Zhao LX, Wang CB, Jin CZ, Qin DG, Pan WS (2009)
Fossil Orangutan-like hominoid teeth from Late
Pleistocene human site of Mulanshan cave in
Chongzuo of Guangxi and implications on taxonomy
and evolution of orangutan. Chinese Sci Bull,
54:3924-3930.
Leaving off the sort of turban of leaves and sticks the creature is wearing, we have what is very likely the earliest depiction of a Didi on record and also very likely one of the best and most straightforeward depictions of the Wildman type, from any time, from anywhere in South America. As mentioned in the earlier blog posting under Maricoxi, for the most part most of the South American "Abominable Snowmen" seem to be of the one type which Ivan Sanderson called Neanderthaloid in his review of the Maricoxi proper, in the scientific journal Genus.
