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Comments on the Theory of Holocene Refugia in the Culture History of AmazoniaAuthor(s): Richard G. WhittenSource: American Antiquity, Vol. 44, No. 2 (Apr., 1979), pp. 238-251Published by: Society for American ArchaeologyStable URL: http://www.jstor.org/stable/279074 .Accessed: 25/04/2011 23:42

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COMMENTS ON THE THEORY OF HOLOCENE REFUGIA IN THE CULTURE HISTORY OF AMAZONIA

Richard G. Whitten

The theory of Holocene refugia in Amazonia as offered by B. J. Meggers is discussed in terms of dating, climate analysis, ecology, and linguistics. There is strong evidence to suggest that Meggers' formulation may be premature.

RECENTLY THERE HAVE BEEN SEVERAL ATTEMPTS at reconstructing the Quarternary pa- leoecology of Amazonian South America. Of interest to archaeologists is Betty J. Meggers' (1974, 1975, 1977) adaptation of a hypothesis developed by J. Haffer (1969, 1974). This hypothesis sug- gests drastic climatic, floral, and faunal discontinuities in the region's past. Meggers' invocation of Haffer's model involves an attempt to explain the distribution and diversity of languages in Amazonia by means of certain migrations in and around posited refugia of tropical vegetation. These comments will summarize Haffer's model and Meggers' adaptation of it, offer some criticisms, and make some alternative suggestions.

Haffer has proposed that the diversity and distribution of avian species in the Amazonian region can only be explained if extreme changes in the ecology are posited (1969, 1974). Specifically Haffer suggests the existence of Pleistocene "refugia," islands of tropical forest sur- rounded by grassland savanna (see Figure 1). These are presumed to have been coeval with glacial periods in the Northern Hemisphere. Normal or interglacial periods saw a return of the forest into the savanna areas. This hypothesis has been accepted by other biologists working in the region (e.g., Vuilleumier 1971; Muller 1973; Vanzolini 1973; Prance 1973; Brown et al. 1974). The sizes and locations of these centers of origin and dispersal vary, however, depending on the species studied (cf. Vanzolini 1973:Figure 1). It should be stated at the outset that actual evidence for any drastic paleofloral changes due to extreme and widespread aridity in Amazonia is prac- tically nonexistent (Van der Hammen 1975).

Even as there is little paleoecological evidence to support this hypothesis, there are arguments that can be made against it. The archaeologist is immediately struck by the similarity of this idea to V. Gordon Childe's oasis theory of domestication. Both utilize a model of extreme ecological change as a deus ex machina to explain changes that otherwise seem unexplainable. The Amazo- nian refugia model can be shown to be a similarly premature attempt. Several flaws, to be discussed in detail below, are already obvious.

Meggers does not refer to any criticism of Haffer's hypothesis. She has simply accepted it and

expanded it to include the presence of refugia during a postulated arid episode in the Holocene

(ca. 4000-2000 B.P.). This use of the concept is in spite of Haffer's own reluctance to apply his model to the ecology of the Holocene (1974:149). Muller (1973) and Vanzolini (1970) do attempt to offer some evidence for such an arid episode, and Meggers' discussion of dating relies on these

secondary sources for documentation (e.g., Meggers 1977:291). Many problems become apparent when such an episode is postulated for the Holocene of

Amazonia. Foremost is the question of timing: when is this episode supposed to have occurred? As will be shown, Meggers' choice of bracketing dates is extremely arbitrary, given even the scarce and contradictory evidence available. Second, Meggers' discussion (like Haffer 1974 and Muller 1973) does not include any modern or critical perspective on the atmospheric mechanisms in- volved in the climate of the region or the mechanisms involved in climate change for the region. Third, Meggers does not take into account the many questions raised by the postulated ecological

Richard G. Whitten, Anthropology Program, Social Behavior Department, University of South Dakota, Ver- million, SD 57069

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Figure 1. Locations of postulated refugia (after Haffer 1969:Figure 5, copyright 1969 by the American Association for the Advancement of Science; Meggers 1977:Figure 4).

changes. There has yet to be a critical discussion of the likelihood of widespread savannas in Amazonia's past or of just what climatological changes would be necessary to bring about such a succession. Finally, recent work on the linguistics of the region calls into doubt the suggested migration pathways chosen by Meggers and concomitantly the very necessity of postulating these refugia.

DATING CLIMATIC EPISODES OF THE HOLOCENE IN AMAZONIA

Compared with most other areas of the world, Amazonian South America is a climatological terra incognita. The nature and timing of Holocene episodes are only now being outlined. This does not mean, however, that an investigator may deal as he or she will with the area. There are already certain constraints placed on the imagination by what is known concerning Holocene climate in areas peripheral to the region and by what is known concerning the nature of climate change in general (Lamb 1966, 1970) and Amazonian climate change in particular (Sanchez and Kutzbach 1974).

Meggers has stated that Amazonia underwent an arid episode during the period 4000-2000 B.P.; as will be shown, it is not at all certain why these particular dates were chosen. By working back through the documentation for the presence of this episode, it can be demonstrated that the investigators upon whom Meggers depends (particularly Muller 1973) have severely misunderstood the evidence necessary for postulating such an episode.

Meggers (1977) and Muller (1973) depend (in part) on a discussion of mean sea level (MSL) changes offered by Fairbridge (1960, 1962) for dating the arid episode. The difficulties inherent in understanding MSL changes as climatic indicators have been outlined by Flint (1971:322-329). Flint makes particular reference to the worldwide data gathered by Fairbridge (1962:Figure 7). More recent work conducted by Milliman and Emery (1968) places Fairbridge's model in some doubt. Milliman and Emery's model of MSL changes does not include the many fluctuations uti-

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lized by Muller in describing a Holocene arid episode (Milliman and Emery 1968:Figures 1 and 2; Fairbridge 1962:Figure 7; Muller 1973:Figure 99).

Whatever the value of Fairbridge's climate chronology, it is not certain whether Muller's use of it to suggest an arid episode during the period 5000-2300 B.P. is a proper one. Unfortunately, ac- cording to his own rendition of the Bigarella (1965) and Fairbridge (1962) MSL change diagram (Muller 1973:Figure 99), this "arid" episode contains the diagram's highest recorded MSL, that is, the "wettest" phase in the Holocene. This date and wet phase (ca. 3800 B.P.) are also included within Meggers' postulated arid episode. The end date chosen by Muller and important for Meg- gers (1977:291) is 2300 ? 220 B.P., or 350 B.C. (Muller 1973:187). The date is attributed to Hurt

(1964); actually, the correct date of 2675 i 150 B.P., or 725 B.C., may be found in Hurt (1964:32). This date is not given as the beginning of te local episode alled the Submergencia Paranaguaense, as Muller believes, but rather as a date for the Abrouhos High contained within that episode (Hurt 1964:32).

Even granting the acceptance of MSL studies as good indicators of gross climatic change worldwide, Muller and Meggers' arid episode cannot now be considered acceptable. Fairbridge (1976) has since continued his work on sea-level changes in Brazil with Hurt (1974) and has of- fered his own view of climatic episodes for Brazil's Holocene. This chronology includes Period V, 3400-2600 B.P. (1976:358), as a "cool and dry" episode, somewhat in conformity with Meggers' prediction. However, Fairbridge also postulates "cool and dry" episodes for Period III, 4800-4100 B.P., and Period VI, 2600-2000 B.P. (1976:357-358). This periodization in no way agrees with the chronologies suggested by Muller and Meggers. Even if Period V were understood to correspond to Meggers' arid episode, it would still be necessary to explain away the previous and succeeding "cool and dry" episodes, since Meggers and Muller argue for only a single Holocene arid episode.

A second form of evidence incorporated by Meggers in the dating of the arid episode is palynological. Climatic discontinuities may be analyzed through well-dated changes in the pollen regime. Palynological research would also seem to be an ideal way to test the refugia hypothesis, since the theory does rest upon fluctuating boundaries between forest and savanna. Forest pollen may be distinguished from savanna pollen types, and such changes in the pollen regime are datable (e.g., Van der Hammen and Gonzalez 1960; Wijmstra and Van der Hammen 1966). The best summary and discussion of palynological studies for northern South America is in Van der Hammen (1975).

It should be kept in mind that pollen studies in the tropics can be problematic. Differential disintegration of pollen grains due to extremes in temperature and precipitation is one concern (Faegri and Iverson 1964). A second concern lies with savanna ecology (discussed in greater detail below): savannas are often artifacts of man's interference with the landscape or the result of changes in local hydrology. Climate changes are not always wise deductions from an influx of savanna-type pollen grains (see Hills and Randall 1968).

Van der Hammen discusses several pollen cores that include dated material relevant to the Holocene and utilized by Meggers (1977:291). The cores have all been taken from areas peripheral to Amazonia (eastern Colombia, Guyana, and west-central Brazil). Thus the particular changes in pollen regime are not analogous to the kinds of ecological changes that may have oc- curred in Amazonia. The climate is not uniform over so large an area (Ratisbona 1976; Snow 1976; Trewartha 1961). The timing of the discontinuities could be thought of as roughly syn- chronous, however, if the carbon dates were consistent among themselves.

In eastern Colombia, Van der Hammen reports on two pollen cores with dates attached. One core is from Lago de Bobos in the Paramo de Guantiva, on the western slope and within the An- dean rainshadow (Cordillera Oriental). Vegetation change in this area would not be analogous to changes on the eastern slope. Van der Hammen reports an influx of paramo-type pollen at approx- imately 3000 B.P. This cool period probably lasted until approximately 800 B.P. The beginning and end of the period are dated by carbon-14 samples (Van der Hammen 1975:13-15, Figure 12). It should be noted that the close of the cool period does not fall at 1990 B.P. as Meggers reports (1977:291). Meggers has depended on a secondary source (Vanzolini 1970:41-42), who in turn

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COMMENTS ON HOLOCENE REFUGIA IN AMAZONIA

depends on an earlier publication of Van der Hammen (1962). Van der Hammen's publication of the original pollen diagram (1975:Figure 12) makes clear the suitability of the 800 B.P. end date.

A second core (this time from the eastern slopes of the Andes) from Colombia was taken from the Laguna de Agua Sucia, south of San Martin. Here Van der Hammen reports "a major period of open savanna, apparently drier than today, which lasted from 6-5000 B.P. to 3800 B.P."

(1975:23). Neither of these disruptions is indicative of Meggers' postulated 4000-2000 B.P. arid episode. Only the second core could have any relevance to Amazonian vegetation change in any case.

In Guyana, Van der Hammen reports on a core taken from Lake Moreiru in the Rupununi savan- na. Here only a single change is noted: savanna pollen begins to dominate ca. 7300 B.P. and con- tinues until the present (1975:21-23, Figure 21). Again there is no evidence for a 4000-2000 B.P. episode, although Meggers (1977:291) does seem to list these cores as evidence. Parenthetically Van der Hammen does not recognize man's influence (probably prehistoric) on the Rupununi savanna, although this has been suggested by Hills (1976).

Finally, in west-central Brazil, Van der Hammen reports on samples taken from near Rondonia. There are no absolute dates reported for these cores. Van der Hammen states: "without reasonable doubt, that there were periods duing the Pleistocene when savannas locally replaced part of the forest" (1975:25, emphasis mine). This is good news for those who, like Haffer, stress the possibility of refugia during the Pleistocene; however, it cannot be used to indicate arid episodes during the Holocene, as Meggers seems to believe (1977:291). In his original report on this material, Van der Hammen reached the same conclusion on the relevance of this information for Pleistocene climates (1972:643).

Palynological research fails to substantiate Meggers' postulated arid episode. A review of available MSL data has also failed. The absolute dates associated with changes in the pollen regimes are neither numerous enough nor consistent enough to suggest the presence of such an episode at this time. In fact there is not a single date that can, under close examination, be used as support for the arid episode.

MECHANISMS FOR CLIMATIC CHANGE IN THE AMAZON BASIN

The one error that all the proponents of refugia in Amazonia make is to assume that climatic change (if and when it did occur) was uniform throughout the region. That is, they assume that the occurrence of an arid episode signifies a uniformly decreased mean annual precipitation over the entire region. Haffer depends upon this assumption to locate his refugia within Amazonia

(1974:144). His own assumption is that:

.. during dry phases rainfall in areas of current maxima of precipitation remained high enough to permit the continued growth of forests, while the forests probably disappeared from the intervening areas of lower rainfall (Haffer 1974:144).

Haffer's justification for this assumption seems to be his belief that orographic features of Amazonia are the primary determinant of the region's precipitation regime; since the orographic features have not changed, the distribution of precipitation in Amazonia has not changed either; only the amounts have changed (1974:144). Meggers accepts the locations of Haffer's Pleistocene refugia as the locations for her own arid Holocene episode (1977:Figure 4). Meggers does not offer any discussion of the region's climatology; so one must assume that she also accepts Haffer's un- derstanding of Amazonian climatology.

The climate of Amazonia is not uniform. Changes do not occur in such a manner that a drop in mean annual precipitation at Belem of, say, 25 mm is concurrent with a similar decrease at Manaus. Teleconnections within the region and between Amazonia and other regions do exist (Bjerknes 1969; Namias 1972; Sanchez and Kutzbach 1974; Wyrkti 1973), but uniform changes of the sort Haffer asserts do not exist and, indeed, cannot exist. A brief description of climatic features for the region is necessary to make this point clear.

The climate of northern South America may be understood as the result of changes in the cir- culation of the planet's atmosphere in conjunction with topography and radiation budget for any

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single area (Lamb 1966, 1970; Trewartha 1961; Ratisbona 1976; Snow 1976). The Intertropical Convergence Zone (ITCZ) is seen as the climatic equator, the fluctuating meeting place of the northern and southern hemispheres' circulatory systems. Its position is seasonally variable, but north and south movement west of the Andes is limited to approximately 5?-7? north latitude (Trewartha 1961:15), although recently the ITCZ has been seen as more variable in position (Flohn 1969:Figure 43). The ITCZ's stability west of the Andes can be understood in terms of the intensity and position of the South Pacific Subtropical High. This cell remains quite constant, only occasionally shifting position or varying in intensity (Hare 1966:Chapter 8). When a change does occur, the ITCZ moves south to northern Peru, causing the meteorological discontinuity known as El Nino years.

East of the Andes, the ITCZ exhibits much more variation in its seasonal movements (Kendrew 1961; Trewartha 1961:Figure 1.18; Ratisbona 1976:Figure 2). The movement of the ITCZ is gener- ally southward over the Amazon Basin from November to March and generally northward (to the Caribbean coast) from December to May (Flohn 1969; Hare 1966: Schwerdtfeger 1976; Barrett 1974). The South Atlantic Subtropical High pressure cell fluctuates in intensity and position in synchrony with these movements (see Figure 2).

The precipitation figures for this region used by Haffer are the result of precipitation brought into Amazonia by the ITCZ during the period 1931-1960 (Reinke 1962). The tropical vegetation of the region is a result of the presence of year-round equatorial air (the ITCZ) and maritime tropical air (the prevailing easterlies), both in conjunction with local soils, hydrology, topography, radia- tion budget, and the region's ubiquitous nonlineal convective precipitation. Vegetation and pre- cipitation on the eastern flanks of the Andes are also determined by altitude (Drewes and Drewes 1957; Beals 1969). One peculiarity in the ITCZ's behavior takes place over the horn of Brazil, the northeast region. Because the region is almost always under the influence of the South Atlantic Subtropical High and the ITCZ passes over only occasionally, less precipitation is received, and the characteristic vegetation is caatingas (dry scrub forest and low brush) (James 1969:722).

The preceding descriptions are based on data gathered before 1960. This is the "normative" understanding of the region's climate. For example, the most acceptable precipitation distribution maps are based on 30-year means: 1931-1960 (Reinke 1962). The worldwide atmospheric circula-

Figure 2. Normal movements of Intertropical Convergence Zone (ITCZ) over South America (approx- imate) (after Trewartha 1961:Figure 1.18, copyright 1961 by the University of Wisconsin).

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COMMENTS ON HOLOCENE REFUGIA IN AMAZONIA

tion system exhibited severely anomalous behavior in the decade 1961-1970. Such anomalous behavior gives the paleoclimatologist an opportunity to view the nature and effects of alternative, probably prehistoric climatic episodes (Bryson 1974). Although the past climates of Amazonia cannot be understood as of either one type or the other (that is, still other alternative climatic pat- terns are possible besides the 1931-1960 and 1961-1970 patterns), an examination of certain conditions in the last decade is constructive for an understanding of the likelihood of refugia.

The last decade has been characterized by, first, a decrease in the intensity of the South Pacific High Pressure cell. This has allowed the ITCZ west of the Andes to drop south and has resulted in a greater frequency of El Nino years for coastal Peru. Second, there have been an increase in the intensity of the South Atlantic High Pressure cell and changes in the intensity of the North Atlan- tic High Pressure cell. The southward trend of the ITCZ over the Amazon Basin seems to have been affected: the area has received markedly less precipitation. A bend in the ITCZ has occurred such that it has been moving over the northeast region of Brazil more frequently, and the area reports an increase of ca. 10% in mean annual precipitation. The east side of the Andes, however, is receiving ca. 10-20% less precipitation (see Figure 3) since the ITCZ fails to pass through as frequently (Namias 1972; Sanchez and Kutzbach 1974; Bryson 1975; and personal in- vestigation of ESSA satellite photographs available at the Center for Climatic Research, Universi- ty of Wisconsin).

Sanchez and Kutzbach (1974) have mapped the mean annual precipitation departures for 1961-1970 (Figure 4). The central portion of Amazonia and the eastern slopes of the Andes are considered to have received approximately 10% less precipitation. The northeast region is seen as having received approximately 10% more precipitation. Sanchez and Kutzbach admit to a low

Figure 3. Postulated abnormal movement of Intertropical Convergence Zone (ITCZ) over South America (1961-1970).

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Figure 4. Amazonian precipitation: departures of 1961-1970 mean annual precipitation from the 1931-1960 mean (after Sanchez and Kutzbach 1974:Figure 1, copyright 1974 by the University of Washington).

density of reporting ground stations but maintain that this pattern is representative of climate

during the Little Ice Age. Overlaying Haffer's postulated refugia locations with this arid episode pattern brings in-

teresting results (Figure 5): refugia disappear in the central region and shrink on the eastern

slopes of the Andes, and new refugia of some sort appear in the northeast region of Brazil. These areas of decreased precipitation would not necessarily have become savanna, although a vegeta- tional response of some kind might be expected-particularly if the departures were great enough to pass a certain threshold (see Hills and Randall 1968:2 and below).

The little information that does exist on the paleoclimate and the mechanisms for climate

change in the region argues against the refugia locations that Haffer and Meggers have chosen.

Although this does not negate all possibilities for refugia in Amazonia's past, Haffer's justifica- tions for the locations are not sufficient. The major orographic features of the Amazonian region have remained constant; such features, however, are only one determinant among many of the climate of the region. It is in fact the changes in these other, atmospheric features that account for and cause climatic change in the region.

VEGETATIONAL CHANGES AND SAVANNA ECOLOGY

Utilizing changes in mean annual precipitation to predict resultant floral communities, as Haf-

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Figure 5. Comparison of suggested refugia locations with precipitation departures (after Haffer 1969:Figure 5, copyright 1969 by the American Association for the Advancement of Science; Sanchez and Kutzbach 1974:Figure 1, copyright 1974 by the University of Washington).

fer and Meggers have attempted, is always very dangerous. This is particularly so in the case of savanna ecologies. Vegetation responds not only to mean annual precipitation but also to the distribution of that precipitation throughout the year, the radiation budget, the local hydrology, and the local soils. Man's interference with the landscape is also a very important aspect of savanna ecology.

Meggers predicts the succession of a natural grassland savanna as a result of a decrease in Amazonia's annual precipitation. There are, however, many ways for a savanna to come about, and in fact a decrease in precipitation is not alone sufficient. Natural savannas in the tropics result from the influence of seasonal extremes in soil moisture, including inundation. For northern

tropical South America the conditions have been described as "unfavorable drainage conditions ... with alternating periods of waterlogging and desiccation" (Beard 1953:203). Forest will not grow under such conditions because few woody species are adapted to these extremes. Until Meggers can provide information on the seasonal variability of precipitation or evidence for drastic changes in Amazonia's hydrology, no strong prediction of a savanna ecosystem succession can be made (for a discussion of the ecology of natural savannas, see Hills and Randall 1968; Walter 1973:67-71).

The fact that natural savannas depend on seasonal changes in soil moisture for their existence makes palynological studies of their succession a problem. Most pollen cores are taken from lake

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bottoms or marshy areas. These are areas where savannas are likely to be of hydrological origin, a result of seasonal flooding. Thus changes in hydrology rather than climate can explain some savanna growth (Denevan 1968:45-47; Peeters 1968:27).

Man's interference with the landscape can also result in a savanna succession. Man may periodically burn off the woody plants (for any number of reasons), introduce grazing animals, or tamper with the area's hydrology, all of which can help bring about the growth and maintenance of a savanna. These savannas are "artificial," or artifacts of man's behavior, and do not depend on climate changes for their existence. Such savannas are widespread in the Old World, and evidence is growing that man has also played a crucial role in the origin, maintenance, and growth of savannas in the New World (e.g., on the role of man's interference in the ecology of the Rupununi savanna in Guyana, see Hills 1976:11-29).

Neither Meggers nor Haffer has discussed the ecology of the postulated tropical forest reserves: the refugia. Arguing against the feasibility of the Brazilian plan for forest reserves in contemporary Amazonia, Gomez-Pompa has stated his belief that such reserves are not large enough to sustain tropical forest floral and faunal communities (Gomez-Pompa et al. 1972). Similarly it can be argued that the small refugia posited by Haffer and Meggers could not long be self-sustaining. The ability of these forest communities to resucceed the savannas is taken for granted; actually, changes in soil texture and soil structure in the interim could militate against this possibility.

Rather than a savanna ecosystem, a decrease in mean annual precipitation for Amazonia can guarantee only a shift in forest type. From the current Tropical Moist Forest (2,000-4,000 mm of annual precipitation), two other forest types could succeed: Tropical Dry Forest (1,000-2,000 mm of precipitation annually) or Tropical Very Dry Forest (500-1,000 mm of precipitation annually). A Tropical Very Dry Forest is made up of deciduous trees, but with a lower biomass than the "rain forest" proper. It is easily cleared by man to form a savanna grassland. A Very Dry Tropical Forest is more open, and grasses may occur. Trees are low and have wide crowns. Again man may interfere to help form a savanna grassland. Both these drier tropical forests are evident in South America; and either of them is an appropriate succession to the contemporary Amazo- nian forest under conditions of decreased mean annual precipitation (Hills and Randall 1968:2).

Predicting the succession of natural savanna from a tropical forest climax under stress from decreased precipitation is a very risky endeavor, and no such savanna growth can be posited until much more paleoecological evidence has been gathered.

LINGUISTIC DIVERSITY IN AMAZONIA

Meggers' purpose in postulating an arid episode with refugia at 4000-2000 B.P. is, I believe, the establishment of an explanatory model for the linguistic diversity apparent in Amazonia. Even if such an arid episode is acceptable (and the episode remains without much strong evidence thus far), it can be shown that Meggers' postulation of the linguistic history of the region is not the only one, or even the most preferable one. Any reconstruction of language changes for the area must be based on glottochronological methods, which, although controversial (see Bergland and Vogt 1962; Hymes 1960), will be utilized here to make certain points. Critical readers should keep Girard's caveat in mind when reviewing any discussion of languages in Amazonia:

While many linguists have shown a penchant for classification of South American languages, attempts to base classification on concrete evidence have been met with considerable resistance (Girard 1971:1).

Meggers' explanation of the linguistic diversity of Amazonia begins first with her assumption of

the breakup of the Ge-Pano-Carib language group at ca. 10,000 B.P. The existence of the Ge-Pano- Carib language was suggested by Greenberg (1960) and is accepted by the World Language List

(Voegelin and Voegelin 1965:42,147-148). Nevertheless, it is a highly tentative Ursprache and not without its critics (see, e.g., Girard 1971:173). I was unable to discover any evidence that this

language underwent divergences ca. 10,000 years ago, as Meggers (1977:294) suggests. If I understand her methodology correctly, she has overlaid a map of the contemporary distribu-

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tion of language groups descended from the hypothetical Ge-Pano-Carib family with a refugia distribution map from Haffer (1969:Figure 5). The result (1977:Figure 7) is claimed to support the

logic of certain migrations. Her distribution of contemporary speakers is based on Mason (1950), whereas more recent work would suggest that modifications are in order (see, for instance, Stark 1977:48-54). This highly tentative reconstruction assumes the linguistic and temporal priority of a refugium in the southeastern part of Amazonia. It could equally well be argued on the same evidence, or lack of it, that the direction of migration be reversed. In fact Meggers cites no evidence to prove the northward direction of migration, nor does she discuss the difficulty or likelihood of such migrations as opposed to migrations along rivers.

Meggers' next attempted correlation between linguistics and climatic discontinuities does in- volve her postulated arid episode. Noble (1965:107) has suggested divergences for the Proto- Arawakan languages at approximately 5000 B.P. Rodrigues (1958:684) has suggested divergences in the Tupian family at the same date. As Meggers admits: "the correlation appears poor" (1977:297) between these dates and her postulated episode of 4000-2000 B.P. She suggests that those dates chosen by Muller (1973) for an arid episode (5000-2300 B.P.) may be correct after all, although she retains her original estimate on the accompanying diagram (1977:Figure 9).

In order to include these linguistic discontinuities within her episode, Meggers next suggests that these divergences may have occurred within the postulated episode if the rate of language change has not remained constant in the past, that is, if the 5000 B.P. date has been erroneously computed (Meggers 1977:297). This, however, goes against the fundamental assumption of glot- tochronology, and certainly no dates can be admissible as evidence for prehistory unless the assumption of a constant rate of change is consistently accepted.

It should be noted here that Noble's (1965) work has been partially invalidated by recent work on Uru-Chipayan by Olsen (1964, 1965; see also Voegelin and Voegelin 1965:11). This work sug- gests that Uru-Chipayan has affinities with Mayan, not Arawakan, and throws into doubt Noble's reconstruction of Proto-Uruan. It also discredits Noble's postulated homeland for Proto- Arawakan. This is in accord with Lathrap's arguments against southeastern Peru as the Ursitz for Arawakan dispersal (1970:70-77). In any case, Meggers' assertion that these two languages share a common homeland in southeastern Peru is also in doubt since, according to Rodrigues (1958:683), the origins for the Tupi family may be found in the Rio Guapore region.

More recent work, superseding that of Noble and Rodrigues, describes a different pattern of time and dispersal for language groups in the region. Stark (1977) has recently completed a lengthy revision and reappraisal of Amazonian linguistic history. Her results appear to be con- gruent with Lathrap's (1970) suggestions concerning prehistoric population movements based on archaeological evidence.

Stark's own glottochronological reckoning describes a divergence of Proto-Arawakan and Tupi- Guaranian at approximately 3730 B.P., similar to the dates offered by Noble and Rodrigues. The center of dispersal chosen by Stark, however, is not similar. Stark postulates a center south of the Amazon River, between the Tapajos and Madeira rivers (Stark 1977:7). This is not an area postulated as an arid episode refugium by either Meggers (1977:Figure 4) or Haffer (1969:Figure 5). As Stark reconstructs the events, Proto-Arawakan diverged at this time, and a northward migration occurred along the Rio Negro (1977:7). Consequent divergences from these two language stocks are further outlined by Stark as occurring in "waves"; the migration paths are seen as primarily along waterways (again, these conclusions are in agreement with Lathrap's re- construction).

Stark's reconstruction is complex, but complete and consistent. No assumed paleoecological discontinuities of mammoth proportions need be called upon, deus ex machina, to explain the diversity and locations of Amazonian languages if reconstructions like Stark's are correct. Mi- gration pathways along watercourses are preferable to Meggers' paths, if only because of what is known of ethnographic evidence on this problem. Migrations along waterways not only are easier but also agree with what is known of the contemporary Indian understanding of river settlement and social prestige. For example, Goldman (1963) has described ethnographic ex- amples of such minimigrations for the Cubeo.

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CONCLUSIONS

In the preceding discussion, I have attempted to criticize, in as organized a manner as possible, the hypothesis of Holocene refugia in Amazonia. Meggers has stated (in what may, after all, be a misprint): "It is unlikely that environmental changes of the magnitude inferred by biologists would have affected human beings" (1977:287). I agree; it is unlikely if only because at this time it is also highly unlikely that the inferences are correct ones for the Holocene ecology of the Amazonian region. Any such environmental changes have yet to be documented. Arguments against the presence of refugia during an arid episode can be summarized in this manner:

1. Evidence for dating such an episode from mean sea level studies is equivocal. The original periodization by Muller and Meggers is rather arbitrary. More recent MSL studies would suggest the presence of oscillations undiscussed by Meggers.

2. Palynological evidence does not support the proposed dates for such an episode. Whereas there is a possibility that one sample suggests forest remission (Rondonia), this probably occurred during the Pleistocene, not the Holocene as Meggers seems to believe.

3. The most recent information on climate change in Amazonia argues against the kind of uniform changes Meggers assumes. Work on alternative climates for the region would suggest that a redistribution of the postulated refugia is necessary (if they ever existed).

4. There needs to be a critical discussion of the exact kinds of climate and hydrology necessary for the natural genesis of savannas. Otherwise this ecosystem cannot be accepted a priori as an alternative to tropical forest during "arid" episodes.

5. Evidence for the linguistic history of the region argues against the necessity for postulating such refugia and any migrations from, around, or into them. Ethnographic evidence argues against such refugia migrations ever having been a popular Amazonian pastime.

Rather than accept Lathrap's (1970) reconstruction of Amazonian prehistory, Meggers has at- tempted to utilize Haffer's model as an alternative explanation. Actually there is very little purely archaeological evidence in the region against which to test either theory.

The best explanations are those that have a certain sense of satisfyingness about them and can- not be demonstrated to be wrong (Ghent 1962a 1962a, 1962b, 1963). If Haffer's assumptions about the climate and ecology of Amazonia were more realistic, this would make Meggers' adaptation of keen interest to prehistorians. If Meggers' own work concerning dating and linguistics in the region were built on a more solid foundation, the attempt would be ingenious and laudatory. Un- fortunately, as this review has attempted to demonstrate, such does not appear to be the case. Lathrap's (1970) reconstruction still stands as th re satisfying explanation for the prehistory of Amazonia.

Acknowledgments. Several individuals have given of their time and patience during the construction of this essay. I wish to thank Dr. Donald Thompson (archaeology), Dr. Louisa Stark (linguistics), Dr. William Denevan (savanna ecology), Dr. J. Kutzbach (climatology), and Mr. Kent Mathewson (cartography), all at the University of Wisconsin. At the University of Illinois, I wish to thank Dr. Wayne Wendland (climatology). All errors in information and judgment nevertheless remain my responsibility. This essay represents Contribution 2 of the South Park Street Geographical Society.

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