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Service utilization among homeless and runaway youth in Los Angeles, California: rates and reasons.

PURPOSE: To describe the service utilization patterns of homeless and runaway youth in a "service-rich" area (Los Angeles, California); identify demographic and other correlates of utilization; and contextualize the findings with qualitative data. METHOD: During Phase 1 of this study, survey data were collected from an ethnically diverse sample of 296 youth aged 13-23 years, recruited from both service and natural "hang-out" sites using systematic sampling methods. During Phase 2, qualitative data were collected from 46 youth of varying ethnicities and lengths of time homeless. RESULTS: Drop-in centers and shelters were the most commonly used services (reported by 78% and 40%, respectively). Other services were used less frequently [e.g., medical services (28%) and substance abuse treatment (10%) and mental health services (9%)]. Utilization rates differed by ethnicity, length of time in Los Angeles, and city of first homeless episode (Los Angeles vs. all others). Shelter use was strongly associated with use of all other services. Despite youths' generally positive reactions to services, barriers were described including restrictive rules, confidentiality and reporting problems, and negative interactions with staff members. Youth suggested improvements including more targeted services, more long-term services, revised age restrictions, and more and/or better job training and transitional services to get them off the streets. CONCLUSIONS: Because shelters and drop-in centers act as gateways to other services and offer intervention potential for these hard-to-reach youth, it is vital that barriers to use of these services are eliminated.

Adolescent↗

Arms races between and within species.

An adaptation in one lineage (e.g. predators) may change the selection pressure on another lineage (e.g. prey), giving rise to a counter-adaptation. If this occurs reciprocally, an unstable runaway escalation or 'arms race' may result. We discuss various factors which might give one side an advantage in an arms race. For example, a lineage under strong selection may out-evolve a weakly selected one (' the life-dinner principle'). We then classify arms races in two independent ways. They may be symmetric or asymmetric, and they may be interspecific or intraspecific. Our example of an asymmetric interspecific arms race is that between brood parasites and their hosts. The arms race concept may help to reduce the mystery of why cuckoo hosts are so good at detecting cuckoo eggs, but so bad at detecting cuckoo nestlings. The evolutionary contest between queen and worker ants over relative parental investment is a good example of an intraspecific asymmetric arms race. Such cases raise special problems because the participants share the same gene pool. Interspecific symmetric arms races are unlikely to be important, because competitors tend to diverge rather than escalate competitive adaptations. Intraspecific symmetric arms races, exemplified by adaptations for male-male competition, may underlie Cope's Rule and even the extinction of lineages. Finally we consider ways in which arms races can end. One lineage may drive the other to extinction; one may reach an optimum, thereby preventing the other from doing so; a particularly interesting possibility, exemplified by flower-bee coevolution, is that both sides may reach a mutual local optimum; lastly, arms races may have no stable and but may cycle continuously. We do not wish necessarily to suggest that all, or even most, evolutionary change results from arms races, but we do suggest that the arms race concept may help to resolve three long-standing questions in evolutionary theory.

Adaptation, Biological↗