Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity.

The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15° S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after ∼800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species.

Chronically unreduced elbow dislocations.

This article focuses on various methods to treat the chronically unreduced elbow. There are only a few small series published in the literature on which to base treatment options. Anatomic features pertinent to the discussion of the chronically unstable elbow are highlighted. The spectrum of treatment options includes open reduction, internal fixation and ligament reconstruction, external fixation, and elbow arthroplasty. The indications, operative technique, and results of each treatment modality are explored.

East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins.

The environmental backdrop to the evolution and spread of early Homo sapiens in East Africa is known mainly from isolated outcrops and distant marine sediment cores. Here we present results from new scientific drill cores from Lake Malawi, the first long and continuous, high-fidelity records of tropical climate change from the continent itself. Our record shows periods of severe aridity between 135 and 75 thousand years (kyr) ago, when the lake's water volume was reduced by at least 95%. Surprisingly, these intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum (LGM), the period previously recognized as one of the most arid of the Quaternary. From these cores and from records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa), we document a major rise in water levels and a shift to more humid conditions over much of tropical Africa after approximately 70 kyr ago. This transition to wetter, more stable conditions coincides with diminished orbital eccentricity, and a reduction in precession-dominated climatic extremes. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but our records provide evidence for dramatically wetter conditions after 70 kyr ago. Such climate change may have stimulated the expansion and migrations of early modern human populations.

Subscapularis tendon tears.

Pathology of the subscapularis tendon is both infrequently identified and not commonly considered as a major source of shoulder pain and dysfunction. Subscapularis tendon pathology can present as isolated tears; partial-thickness tears; anterosuperior tears, also involving the supraspinatus tendon; complete rotator cuff avulsion; and rotator interval lesions, in which instability of the long head of the biceps tendon may dominate the clinical presentation. Although an accurate physical examination is paramount, modalities such as arthroscopy, magnetic resonance imaging, and ultrasound have advanced knowledge of the spectrum of abnormalities involving the subscapularis tendon. Nonsurgical management may be effective for most partial tears. Surgically, open repair is more frequent than use of arthroscopic techniques. Tears of the subscapularis tendon portend a different prognosis than do supraspinatus tendon tears, especially when the injury is acute and diagnosis is delayed.