From 1982 through 1987, the American Foundation for the Study of Man (AFSU) conducted archaeological investigations on or near the ancient biblical spice routes in the Wadi al-Jubah area in eastcentral Yemen. Most of this volume is devoted to pedological and geomorphological research undertaken during the 1987 field season. The primary objective was to demonstrate how pre-Islamic and recent land use, especially flood (seil) irrigation farming, modified the environment of the study area.
The volume is organized in six parts, with each part containing one or more "articles." A gazetter, glossary, and introduction precede Part I. The first article (Part I) is a brief summary of an interview with a sheik of the Baltarith tribe who provides a first-hand account of agricultural practices in the study area since the early 1900's.
Part II consists of six articles, three of which concentrate on landforms and soils resulting from seil irrigation. Maurice J. Grolier provides a detailed geomorphic inquiry into seil processes and seil irrigation farming in the al-Jadidah basin of Wadi al-Jubah. He notes that the archaeological evidence suggests a 1700-year gap between pre-Islamic seil irrigation and modern resettlement of the basin in the 19th century. Possible relations between the decay of ancient seil irrigation and changes in climate and the hydraulic geometries of wadis and irrigation canals are considered. However, the geomorphic and stratigraphic evidence does not indicate that abandonment of pre-Islamic agriculture was related to natural causes. Instead, Grolier argues that expansion of agriculture to ever higher interfluves, plus the gradual rise of the tilled surface above present-day Wadi beds, made the canal network unstable and led to its failure.
Grolier's essay sets the stage for the next article, "Pedological Characteristics of Anthrosols in the al-Jadidah Basin of Wadi al-Jubah, and Native Sediments in Wadi al-Ajwirah, Yemen Arab Republic," by Robert Brinkmann. Brinkmann's article is the largest component of the book and could easily stand alone. The purpose of his investigation was to determine the nature and extent of the pre-Islamic human alteration of the soil ecology. Most of the article consists of detailed descriptions of 12 soil profiles formed in anthropic cumulic Fluvents, buried Mollisols, naturally formed Fluvents, and irrigation channel deposits in the Wadi al-Jubah area. Each soil-profile description composes a section of the article and is accompanied by the results of physical and chemical laboratory analyses and interpretations of the data. Also, radiocarbon ages are presented for some soil profiles. Brinkmann concludes that the soil ecology underwent three major changes during the Holocene, two of which resulted from climatic fluctuations and one, the latest, from prehistoric agricultural activity. The period from ca. 10,000 to 6000-5000 B.P. was characterized by aridity and concomitant eolian and fluvial sedimentation punctuated by episodes of relatively moist conditions and associated soil (Mollisol) development. The modern arid climate was in place sometime between 6000 and 5000 B.P. Deposition of irrigation sediment and development of anthropic cumulic Fluvents began around 3300 B.P. and continued to at least ca. 2500-2400 B.P. The results of the chemical analyses indicate that the anthrosols formed under drier conditions compared to the early Holocene environment that favored the development of Mollisols in the region. VOL. 13, NO. 7
Brinkmann concludes his article with a list of recommendations for future pedological and geoarchaeological investigations. He emphasizes the need for archaeologists to explore the period covering the onset of grazing activity and the arrival of irrigation agriculture in the region. Such an approach is necessary to test the hypothesis that desertification was promoted by overgrazing around 6000 B.P. and that irrigation agriculture resulted from technological adaptations to a stressed food-production system. Brinkmann notes that clues to the cultural history of preirrigation residents are likely to be contained in the Mollisols beneath the agricultural deposits.
In the next article, Brinkmann briefly describes an attempt to use thermoluminescence (TL) dating to determine the absolute age of the pre-Islamic anthrosols in Wadi al-Jubah. Clarification of the time of formation of the anthrosols is needed to improve our understanding of the history of irrigation in the region. The TL dating, however, was unsuccessful. Brinkmann attributes the negative results to the grain size (sandy silts) of the samples.
Article 5, "Sites and Structures of Hujran al-Kanus (HK25), Yemen Arab Republic," is by Niki R. Clark and Jeffrey A. Blakely. Discovered in 1982, the Hujran al-Kanus sites and associated silt fields are among the best preserved ancient irrigation installations, ancient fields, and rural occupations in the project area. Clark and Blakely provide detailed site plans of irrigation structures, mound sites, and wells. Excellent photographs of the archaeological features accompany the site plans. However, the reader is left wondering about the age of the sites since no temporal information is given.
Maurice J. Grolier prepared the next article, "Plate Tectonics and Climate Modification and Disruption of Drainage in Southwestern Arabia and the al-Jadidah Basin, Wadi al-Jubah, Yemen Arab Republic." First, Grolier integrates a discussion of plate tectonics (continental drift) and uplift of the Arabian Shield and its Red Sea and Gulf of Aden margins with a description of past regional drainage changes in Yemen. Next, he considers the effects of Quaternary climatic change on stream flow in Wadi al-Jubah. Finally, Grolier describes the incipient capture of Wadi al-Jubah by a tributary of Wadi Mala in the al-Jadidah basin. He concludes that the 2000 m uplift of the Arabian Shield, which followed rifting in the Red Sea and Gulf of Aden structural depressions more than 13 million years ago, and the change in global and regional climate after the Climatic Optimum about 6000 years ago, "stand out as the two events, so far apart in time as they are, that conditioned and contributed most to the eventual development of seil agriculture in the Wadi al-Jubah basin." Grolier also stresses that stream capture threatens the modern seil irrigation agriculture in the southeastern part of the al-Jadidah basin.
The last article in Part II, "Late Pleistocene Mollisol and Cumulic Fluvents near Ibb, Yemen Arab Republic," is by Brinkmann and Abdu O. Ghaleb. Two buried Mollisols were examined in a roadcut south of Ibb. Bulk organic carbon from the upper and lower paleosol yielded radiocarbon ages of ca. 19,300 and 26,150 B.P., respectively. Brinkmann and Ghaleb compared some of the physical and chemical properties of these late Pleistocene paleosols with the properties of the Holocene-age Mollisols in the Wadi al-Jubah area.
Part III consists of three articles that focus on organic evidence related to the environment of Wadi al-Jubah. In the first article, Brian Hesse uses the faunal record from strata at Hajar ar-Rayhani to assess pastoral exploitation in Yemen during the Iron Age. Variations in the abundance of sheep, goats, cattle, and camel remains suggest that exploitation patterns oscillated during the period of occupation at the site. The next article is by William C. Overstreet and James C. Ritchie, presenting the results of pollen analyses on 12 sediment samples collected from the Wadi al-Jubah area. Unfortunately, the sediments yielded such low and erratic distributions of identifiable pollen that reliable statistical results were not obtained. The last "article" in Part III is actually a summarized species list for the botanical remains recovered at Hajar ar-Rayhani during the 1987 excavations. The list, which was prepared by Robert B. Stewart, supplements and expands on previous reports covering excavated botanical remains in the Wadi al-Jubah area.
Part IV consists of a brief article by Dan Rahimi that describes and interprets lithic artifacts discovered during 1987 reconnaissance of the Wadi al-Jubah area. Thirteen localities yielded lithic material, largely obsidian but including a small amount of flint.
Part V consists of two articles that describe sites that were found outside the project area. In the first